diff --git a/Build/scripts/add_msbuild_path.cmd b/Build/scripts/add_msbuild_path.cmd
index e53f1a3beae..b2620d9ecf2 100644
--- a/Build/scripts/add_msbuild_path.cmd
+++ b/Build/scripts/add_msbuild_path.cmd
@@ -6,11 +6,12 @@
 :: add_msbuild_path.cmd
 ::
 :: Locate msbuild.exe and add it to the PATH
-set USE_MSBUILD_12=%1
 
-if "%USE_MSBUILD_12%" == "True" (
-    echo Skipping Dev15 and trying Dev12...
-    goto :LABEL_USE_MSBUILD_12
+set FORCE_MSBUILD_VERSION=%1
+
+if "%FORCE_MSBUILD_VERSION%" == "msbuild14" (
+    echo Skipping Dev15 and trying Dev14...
+    goto :LABEL_USE_MSBUILD_14
 )
 
 where /q msbuild.exe
@@ -20,8 +21,10 @@ if "%ERRORLEVEL%" == "0" (
 
 REM Try Dev15 first
 
-set MSBUILD_VERSION=15.0
+echo Trying to locate Dev15...
 
+:LABEL_USE_MSBUILD_15
+set MSBUILD_VERSION=15.0
 set "MSBUILD_PATH=%ProgramFiles(x86)%\Microsoft Visual Studio\Preview\Enterprise\MSBuild\15.0\Bin"
 
 if not exist "%MSBUILD_PATH%\msbuild.exe" (
@@ -40,8 +43,9 @@ if exist "%MSBUILD_PATH%\msbuild.exe" (
     goto :MSBuildFound
 )
 
-echo Dev15 not found, trying Dev14...
+echo Dev15 not found, trying to locate Dev14...
 
+:LABEL_USE_MSBUILD_14
 set MSBUILD_VERSION=14.0
 set "MSBUILD_PATH=%ProgramFiles%\msbuild\%MSBUILD_VERSION%\Bin\x86"
 
@@ -53,25 +57,6 @@ if not exist "%MSBUILD_PATH%\msbuild.exe" (
     set "MSBUILD_PATH=%ProgramFiles(x86)%\msbuild\%MSBUILD_VERSION%\Bin\amd64"
 )
 
-if exist "%MSBUILD_PATH%\msbuild.exe" (
-    goto :MSBuildFound
-)
-
-echo Dev14 not found, trying Dev12...
-
-:LABEL_USE_MSBUILD_12
-set MSBUILD_VERSION=12.0
-set "MSBUILD_PATH=%ProgramFiles%\msbuild\%MSBUILD_VERSION%\Bin\x86"
-echo Dev14 not found, trying Dev %MSBUILD_VERSION%
-
-if not exist "%MSBUILD_PATH%\msbuild.exe" (
-    set "MSBUILD_PATH=%ProgramFiles(x86)%\msbuild\%MSBUILD_VERSION%\Bin"
-)
-
-if not exist "%MSBUILD_PATH%\msbuild.exe" (
-    set "MSBUILD_PATH=%ProgramFiles(x86)%\msbuild\%MSBUILD_VERSION%\Bin\amd64"
-)
-
 if not exist "%MSBUILD_PATH%\msbuild.exe" (
     echo Can't find msbuild.exe in "%MSBUILD_PATH%"
     goto :SkipMsBuildSetup
@@ -81,7 +66,7 @@ if not exist "%MSBUILD_PATH%\msbuild.exe" (
 echo MSBuild located at "%MSBUILD_PATH%"
 
 set "PATH=%MSBUILD_PATH%;%PATH%"
-set USE_MSBUILD_12=
+set FORCE_MSBUILD_VERSION=
 set MSBUILD_PATH=
 
 :SkipMsBuildSetup
diff --git a/Build/scripts/locate_msbuild.ps1 b/Build/scripts/locate_msbuild.ps1
index bfde99e9ad0..d0e4e1f4bb2 100644
--- a/Build/scripts/locate_msbuild.ps1
+++ b/Build/scripts/locate_msbuild.ps1
@@ -68,14 +68,6 @@ function Locate-MSBuild() {
         return $msbuildExe
     }
 
-    $_ = WriteMessage "Dev14 not found, trying Dev12..."
-
-    $msbuildExe = Locate-MSBuild-Version("12.0")
-    if ($msbuildExe -and (Test-Path $msbuildExe)) {
-        $_ = WriteMessage "Found `"$msbuildExe`""
-        return $msbuildExe
-    }
-
     WriteErrorMessage "Can't find msbuild.exe."
     return "" # return empty string
 }
diff --git a/netci.groovy b/netci.groovy
index 9b71d63134f..ceec424efea 100644
--- a/netci.groovy
+++ b/netci.groovy
@@ -18,18 +18,32 @@ def msbuildTypeMap = [
 
 // convert `machine` parameter to OS component of PR task name
 def machineTypeToOSTagMap = [
-    'Windows_NT': 'Windows',        // Windows Server 2012 R2, equivalent to Windows 8.1 (aka Blue)
+    'Windows 7': 'Windows 7',       // Windows Server 2008 R2                     ~= Windows 7
+    'Windows_NT': 'Windows',        // 'latest-or-auto' -> Windows Server 2012 R2 ~= Windows 8.1 aka Blue
+                                    // 'latest-dev15-5' -> Windows Server 2016    ~= Windows 10 RS2/RS3, with Dev15.5
     'Ubuntu16.04': 'Ubuntu',
     'OSX': 'OSX'
 ]
 
+def defaultMachineTag = 'latest-or-auto'
+def defaultWindowsMachineTag = defaultMachineTag
+def defaultXPlatMachineTag = defaultMachineTag
+
+def legacyWindowsMachine = 'Windows 7'
+def legacyWindowsMachineTag = defaultMachineTag
+def legacyWindowsTestExtra = '-win7'
+
+def latestWindowsMachine = 'Windows_NT'
+def latestWindowsMachineTag = 'latest-dev15-5'
+def latestWindowsTestExtra = '-win10'
+
 def dailyRegex = 'dailies'
 
 // ---------------
 // HELPER CLOSURES
 // ---------------
 
-def CreateBuildTask = { isPR, buildArch, buildType, machine, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup ->
+def CreateBuildTask = { isPR, buildArch, buildType, machine, machineTag, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup ->
     if (excludeConfigIf && excludeConfigIf(isPR, buildArch, buildType)) {
         return // early exit: we don't want to create a job for this configuration
     }
@@ -75,7 +89,7 @@ def CreateBuildTask = { isPR, buildArch, buildType, machine, configTag, buildExt
         false, // doNotFailIfNothingArchived=false ~= failIfNothingArchived
         false) // archiveOnlyIfSuccessful=false ~= archiveAlways
 
-    Utilities.setMachineAffinity(newJob, machine, 'latest-or-auto')
+    Utilities.setMachineAffinity(newJob, machine, machineTag ?: defaultWindowsMachineTag)
     Utilities.standardJobSetup(newJob, project, isPR, "*/${branch}")
 
     if (nonDefaultTaskSetup == null) {
@@ -95,11 +109,11 @@ def CreateBuildTask = { isPR, buildArch, buildType, machine, configTag, buildExt
     }
 }
 
-def CreateBuildTasks = { machine, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup ->
+def CreateBuildTasks = { machine, machineTag, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup ->
     [true, false].each { isPR ->
         ['x86', 'x64', 'arm'].each { buildArch ->
             ['debug', 'test', 'release'].each { buildType ->
-                CreateBuildTask(isPR, buildArch, buildType, machine, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup)
+                CreateBuildTask(isPR, buildArch, buildType, machine, machineTag, configTag, buildExtra, testExtra, runCodeAnalysis, excludeConfigIf, nonDefaultTaskSetup)
             }
         }
     }
@@ -142,7 +156,7 @@ def CreateXPlatBuildTask = { isPR, buildType, staticBuild, machine, platform, co
         true, // doNotFailIfNothingArchived=false ~= failIfNothingArchived (true ~= doNotFail)
         false) // archiveOnlyIfSuccessful=false ~= archiveAlways
 
-    Utilities.setMachineAffinity(newJob, machine, 'latest-or-auto')
+    Utilities.setMachineAffinity(newJob, machine, defaultXPlatMachineTag)
     Utilities.standardJobSetup(newJob, project, isPR, "*/${branch}")
 
     if (nonDefaultTaskSetup == null) {
@@ -213,7 +227,7 @@ def CreateStyleCheckTasks = { taskString, taskName, checkName ->
             Utilities.addGithubPushTrigger(newJob)
         }
 
-        Utilities.setMachineAffinity(newJob, 'Ubuntu16.04', 'latest-or-auto')
+        Utilities.setMachineAffinity(newJob, 'Ubuntu16.04', defaultXPlatMachineTag)
     }
 }
 
@@ -221,34 +235,45 @@ def CreateStyleCheckTasks = { taskString, taskName, checkName ->
 // INNER LOOP TASKS
 // ----------------
 
-CreateBuildTasks('Windows_NT', null, null, "-winBlue", true, null, null)
+CreateBuildTasks(latestWindowsMachine, latestWindowsMachineTag, null, null, latestWindowsTestExtra, true, null, null)
 
 // Add some additional daily configs to trigger per-PR as a quality gate:
 // x64_debug Slow Tests
 CreateBuildTask(true, 'x64', 'debug',
-    'Windows_NT', 'ci_slow', null, '-winBlue -includeSlow', false, null, null)
+    latestWindowsMachine, latestWindowsMachineTag, 'ci_slow', null, "${latestWindowsTestExtra} -includeSlow", false, null, null)
 // x64_debug DisableJIT
 CreateBuildTask(true, 'x64', 'debug',
-    'Windows_NT', 'ci_disablejit', '"/p:BuildJIT=false"', '-winBlue -disablejit', false, null, null)
+    latestWindowsMachine, latestWindowsMachineTag, 'ci_disablejit', '"/p:BuildJIT=false"', "${latestWindowsTestExtra} -disablejit", false, null, null)
 // x64_debug Lite
 CreateBuildTask(true, 'x64', 'debug',
-    'Windows_NT', 'ci_lite', '"/p:BuildLite=true"', '-winBlue -lite', false, null, null)
+    latestWindowsMachine, latestWindowsMachineTag, 'ci_lite', '"/p:BuildLite=true"', "${latestWindowsTestExtra} -lite", false, null, null)
+// x64_debug Legacy
+CreateBuildTask(true, 'x64', 'debug',
+    legacyWindowsMachine, legacyWindowsMachineTag, 'ci_legacy', 'msbuild14', "${legacyWindowsTestExtra} -includeSlow", false, null, null)
 
 // -----------------
 // DAILY BUILD TASKS
 // -----------------
 
 if (!branch.endsWith('-ci')) {
-    // build and test on the usual configuration (VS 2015) with -includeSlow
-    CreateBuildTasks('Windows_NT', 'daily_slow', null, '-winBlue -includeSlow', false,
+    // build and test on the legacy configuration (Windows 7 + VS 2015 (Dev14))
+    CreateBuildTasks(legacyWindowsMachine, legacyWindowsMachineTag, 'daily_legacy', 'msbuild14', "${legacyWindowsTestExtra} -includeSlow", false,
+        /* excludeConfigIf */ { isPR, buildArch, buildType -> (buildArch == 'arm') },
+        /* nonDefaultTaskSetup */ { newJob, isPR, config ->
+            DailyBuildTaskSetup(newJob, isPR,
+                "Windows 7 ${config}",
+                'legacy\\s+tests')})
+
+    // build and test on the latest configuration (Server 2016 + VS 2017 (Dev15)) with -includeSlow
+    CreateBuildTasks(latestWindowsMachine, latestWindowsMachineTag, 'daily_slow', null, "${latestWindowsTestExtra} -includeSlow", false,
         /* excludeConfigIf */ null,
         /* nonDefaultTaskSetup */ { newJob, isPR, config ->
             DailyBuildTaskSetup(newJob, isPR,
                 "Windows ${config}",
                 'slow\\s+tests')})
 
-    // build and test on the usual configuration (VS 2015) with JIT disabled
-    CreateBuildTasks('Windows_NT', 'daily_disablejit', '"/p:BuildJIT=false"', '-winBlue -disablejit', true,
+    // build and test on the latest configuration (Server 2016 + VS 2017 (Dev15)) with JIT disabled
+    CreateBuildTasks(latestWindowsMachine, latestWindowsMachineTag, 'daily_disablejit', '"/p:BuildJIT=false"', "${latestWindowsTestExtra} -disablejit", true,
         /* excludeConfigIf */ null,
         /* nonDefaultTaskSetup */ { newJob, isPR, config ->
             DailyBuildTaskSetup(newJob, isPR,
diff --git a/test/jenkins.build.init.cmd b/test/jenkins.build.init.cmd
index 9d9cc836046..0228cc1b43f 100644
--- a/test/jenkins.build.init.cmd
+++ b/test/jenkins.build.init.cmd
@@ -13,11 +13,11 @@ if not "%JENKINS_BUILD%" == "True" (
 set REPO_ROOT=%~dp0\..
 
 set JENKINS_BUILD_ARGS=
-set JENKINS_USE_MSBUILD_12=
+set JENKINS_FORCE_MSBUILD_VERSION=
 :ContinueArgParse
 if not [%1]==[] (
-    if [%1]==[msbuild12] (
-        set JENKINS_USE_MSBUILD_12=True
+    if [%1]==[msbuild14] (
+        set JENKINS_FORCE_MSBUILD_VERSION=%1
         goto :ContinueArgParseEnd
     )
 
@@ -36,4 +36,4 @@ if not [%1]==[] (
 :: Set up msbuild.exe
 :: ========================================
 
-call %REPO_ROOT%\Build\scripts\add_msbuild_path.cmd %JENKINS_USE_MSBUILD_12%
+call %REPO_ROOT%\Build\scripts\add_msbuild_path.cmd %JENKINS_FORCE_MSBUILD_VERSION%