Would changing the version in the XML file work? Worth a try. Oh, and make sure you have a backup copy.
If I recall, though, there were some significant changes between 95 and 99 that involved changing some properties... Might cause issues.
Edit the .caproj file and fix this line:
<saved-with-version>9900</saved-with-version>
To 9500 or something, I think. Good luck!
P.S.: If you manage to open it, do "save as" and save it as a brand new project that should deal with any artifacts from 99.