Corrupted core files?

Dunno what happened, but it seemed that several files in my “C:” disk got corrupted after my Users folder mysteriously disappeared. I used system restore to get it back, but many of the programs still won’t run properly, including: Adobe Photoshop (Microsoft Visual C++ Runtime Library Error), Search Control Panel/toolbar (Do not have the appropriate permission to access the specified device, path or file), the Opera (Access denied due to insufficient resources or locked files). I can’t even defragment the disk properly without freezing up the whole explorer, and forcing me to restart. Can anyone help?

P.S. I thought this problem was caused by the missing AppData/Roaming folders I asked about previously, but apparently, it was something else - though I don’t know what that something else is.