Hi all
Actually, the method that was successful for LordTreant has proven to be one of the methods with the best chance of success on first try. It works whether or not you have corrupted system files, corrupted profiles, tangled drivers ...
If you consider the amount of time that can be spent trying to find the magic bullet for your exact issue, it might turn out that the online in-place repair "upgrade" reinstall saves you time: simply because it works.
Run diagnostics on your hardware, though, before trying an in-place reinstall ..... software fixes can't do anything to fix hardware problems. Run malware scans beforehand too.