I had the same problem, 2 days ago in fact. I read it could be a registry problem. Scan registry and found over 1000 errors, mainly problems w/ bad installs/uninstalls. Unfortuneatly had to reboot/boot/reload (what ever name you give it), but not too bad a prob. amazing how fast the boot was, i remember rebooting on Me (millenium edition) and would of been cheaper to go in to town, to internet cafe, order a new pc and wait for delivery.
Also, if u can, try to move things like, photos, important music files etc. (memories mainly) onto and extrenal hard drivein safe mode before boot.
****-----**** Hate to bump this old post but with the amount of dodgy software about, registry problems are unfortuneatly common these days.****-----****