Unable to delete file

[Terry]

Sometimes I just can't friggin delete a file. (mostly .avi)

When I try to delte it, it says it is being "used by another person or program"

I have restarted the computer and stuff like that, trying to look for weird processes that might still be using the file, but with no luck.

I also tried Norton's Wipe Info.
That didn't work either.

??

edit: are there utilities out there that will tell me what programs are accessing the file?

edit2: ok, I ran the Wipe Info again and it worked.
But what was the reason? Any insights?