The answer is in one of the Q & A's (by zendu)
Copy the files from
%APPDATA%..\Local\Microsoft\MSBuild\SlowCheetah\v1.
to
%APPDATA%..\Local\Microsoft\MSBuild\SlowCheetah\v2.5.10.
List of files:
Install-Manifest.xml
Microsoft.Web.XmlTransform.dll
SlowCheetah.Tasks.dll
SlowCheetah.Transforms.targets
SlowCheetah.Xdt.dll
Also see this related question
The "SlowCheetah.Xdt.TransformXml" task could not be loaded from the assembly