I created a backup. Now, I deleted Skyrim (had major problems with mods) and decided to restore my Skyrim backup (which I saved at the C: drive)

to my surprise, got the message:

Validating Steam Files 100% Complete
189 files failed to validate and will be reaquired.



its probably the 4th damn time I have to redownload the whole Skyrim plus Dawnguard + Textures. (two times were before doing a backup, 3rd time I had done a backup and went for the restore option, then went away from the computer while it was validating the files. A few hours later I came back and it was finishing dowloading the files again, but I never understood why (apparently, the files failed to validade)