Monty Python

I agree the most likely culprit is malware, given the heavy torrent usage, however the lag in assistance in Securities is long, so continuing to troubleshoot until definative malware presence is found is advised.

The "file locked & inaccessable" message in NOD32 is normal.\

The inability to manipulate files is normal if UAC is turned on.

I wouldn't jump right into a reformat & reinstall just yet, as that may pose more difficult problems than what you already have.

What were the most serious of the Event Viewer errors ? Sometimes a pattern can be discerned. A screen shot might be helpful.

What was the BSOD message ? Sometimes they point to a specific device driver, such as video ?

Run MSCONFIG and selectively turn off all non-essential programs. The intent is to see if turning things off returns functionality to other things. this will require some good thinking & trial & error.

Check Device Manager, make sure to enable "show hidden devices". Uninstall any flagged items & reinstall. Make note of any flagged items & report them here. Pay close attention to virtual device drivers, like Nero, Daemon Tools, etc....

Also, it might be constructive to run chkdsk /f.