Been using cakewalk Sonar 7 for a while and got some projects done and saved. Normally enter a project after opening Sonar .I visited an earlier project .Then my current project was not in the list. Tried to access from C drive. It loaded up but stated some audio cannot be found replaced with silence .I now have the project but no detail. The wav files are in the project audio but it says they are missing. The files are also in the picture cache. From Drive C cakewalk projects there is now no audio file but it did say it was empty. I have not deleted anything. The rest of my projects work fine. just lost sound/detail on this one .All help appreciated.

If it was me i would just take the first missing audio files name and search all drives for it.
 
Hope you sort it

Whenever I've gotten the "missing audio" dialog, it's been because the project referenced files that weren't in the Audio folder under the .cwp file. You may have some wave files, perhaps loops or samples, that are external to the project and have been deleted or moved since you last loaded it.
 
A project normally contains dozens of files, so it may look as though everything is there even if one or two files are missing. When the missing-audio dialog comes up, note one of the pathnames it's looking for and do a global search for it, as suggested by SiTheMon. Either you'll find it in an unexpected place, in which case you can then copy it to where the project expects it to be, or you won't find it, in which case the file's been deleted and you're outa luck.
 
Is it possible that one or more files is on an external drive that's no longer connected?

Project > Audio Files lists all files used in the project, their locations, bit depth, edits, file size, and perhaps most importantly, whether the file is Local. This means the file is stored in the per-project audio file, so when you save or copy the project folder, all audio will travel with it. Global means the file is stored in the Global Audio Data directory, External means it’s stored somewhere other than Cakewalk project folders (e.g., on a CD-ROM sample library), and Missing...well, that means SONAR can’t find the file.
 
For more details see my Friday's Tip of the Week #66.