Could be a whole bunch of things....but, I just had the same problem with a back up computer. One of the attached CDRW's failed. You probably have a malfunctioning component and it's either a floppy or cdr I would suspect. Unplug the power from your floppy and cdrom's, dvd rom and then power you puter back up. If it boots up quickly...there ya go....one of those components needs to become a frisby! If not that?????????? window reinstall maybe, as stated above. EDIT: the psu remains a good possibility as well.
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