Post your computer specs. That could be many things.
If it's not hardware it could be just a bad or damaged boot sector on your hard drive a or missing windows files. Try to hit F8 repeatedly while the computer is booting until it sets to the menu with options on starting the computer. select last known good configuration and let it reboot. If this doesnt work start over with the F8 back in the many select safe mode without network support. See if that gets you into windows. If so then go into help right column 2nd up from bottom system restore and restore to an earlier time.
