Verified answer

Run your restore disc if you have one, otherwise do a fresh install of your OS.

its a possibility you could have a worm in your system. when i had a worm it wouldnt allow me to deleate anything. by using thr right click.

do you run your computer 24/7? try shutting down the computer, wait one minute then turn it back on. everything should go back to normal if nothing happens you may have recover to an earlier date. if that dosnt work then you ganna have to do a total system recover from another drive or with the cd's that came with your computer. back up everything first before you run recovery. recovery will deleate anything thats on the hard drive and will put the computer as if you just bought it.

good luck!