Recently, I noticed it was very difficult to delete pictures I had saved in the normal folder. It would sometimes take minutes and different mouse clicks to delete them. Also, scrolling thru text on e-mail, DG and cubits would lock up for a second or two then jump. Being the old time computer person I am, I deleted the active partition, did the slow format bit, and reinstalled Vista with only the basics added. Norton 360, OEM ATI video drivers, SP-1, SP-2, IE9 and an additional 112 Windows update files. Everything worked fine then I added Adobe Reader 10 and Adobe Flash 11. Still, everything works great with a pic delete in 1 second or so.
I can't explain the problem but I am certain it was either a virus of some kind or a Windows update which messed up the video driver or mouse driver. I can blame my wife, she isn't sitting here, for possibly clicking onto something in Facebook or the coupon site she likes to surf. Last year, I had a Windows update which messed up the CD/DVD driver.
The point is don't be afraid to scrub your pc clean and start over. Most pcs need to be erased and reformatted once a year just to eliminate the clutter. It is a good idea to partition a large drive to a size required for the OS and device drivers with an ample amount left over for future addons and virtual memory. My 'C' drive was 250gb and I partitioned it as a 50gb active drive leaving the 200gb partition for programs. A 750gb drive is used for junk storage and backup.
Just as info, everything began working perfectly after reformatting and reloading the programs I had previously. Hasn't skipped a beat since. Not certain of the cause but it is possible some kind of trojan slipped by my AV. Most likely it was a Microsoft update although I found the version of IE I was running was a beta version and a newer version was installed after the reformatting.