In the registry
- [HKEY_CURRENT_USER\Software\Microsoft\VisualStudio{VisualStudioVersion}_Config\Projects\
- [HKEY_CURRENT_USER\Software\Microsoft\VisualStudio{VisualStudioVersion}_Config\Packages\
The Project TypeId from the project file can be used to find the relevant information under the first registry path. If further information is required you can for the "Package" key searching under the second registry path.
ps. {VisualStudioVersion} must be substituted with the version you are checking against ie. 10.0 (2010) or 11.0 (2012)