Computer partially boot up...then freezes

Hi...I replaced my Power Supply and when I powered up my computer it acts like it is going to boot up...(running Windows XP) I get the Windows XP Home edition screen with the bar at the bottom...it cycles through the bar maybe three times and then it goes to a "message no signal box" and then it goes to a blank screen and it does nothing...I would think the monitor is good since I get the XP screen...I can get to the BIOS settings. I am running with a Pentium 4 1.7 GHZ CPU. Any help would be appreciated. Thanks.
Mavrik19

If POST does not give you two beeps or more, then your hardware is fine. However, since Windows does not seem to boot, you could try repairing the boot sector for starters.

Here is what I would normally do (it is up to you to find the same resources):
Remove your hard drive and set it up as a slave drive on another computer (or get the hard drive from another computer and set it up as master on yours and set up the original hard drive as the slave).
Get a copy of Norton Systemworks (you will use Norton Disk Doctor and WinDoctor) on CD and put it into the CD-ROM drive. It should automatically run. Launch utilities from the CD and run Disk Doctor, then WinDoctor to help find and repair all problems.
Upon completion of first sweep of scans, run them one more time for good measure. When done, try booting to the original hard drive again to see if it helped.

If this procedure does not work, then set up the original HD as a slave drive once more and begin the backup process. I personally do not have any other ideas other than to reinstall the operating system. Again, I emphasize backing up your files, including pictures, music, documents, spreadsheets, databases, saved games, downloaded software (setup files), etc. if they must be preserved. That way, if more problems seem arise, your data is okay.