I would suggest the following:
Try and boot into safe mode - if Windows boots up then I would say its a problem with a corrupted driver of somesort. Remove any USB devices attached and try to start windows normally. If it displays the same symptons then:
Find a Windows disk (preferably a full installation disk, rather than a ghost image of how the system was built at the factory as this will clear out everything)
Let it load up and when prompted with the options chose 'R' for the recovery console.
Once there choose the HDD or partition that has windows on it (by default there should only be one). Press 1 to access it, you should then have a block square and will look similar to DOS.
Type in chkdsk /p this should generally recover and restore any files that may have become corrupted for whatever reason. This can take some time so best to do it when your not in a hurry. Once its complete then I would reboot the system and see if you can access Windows again. If after a few hours or so the system is still trying to recover data, then just reboot it anyway; however it would be very much 50/50 as to whether it works or not.
Failing all of these I would have to say that Windows has had its day and you will need to reinstall from scratch.
I hope this helps
Urban Kaos, November 2007