On any system that old you can easily run into multiple problems at once. bad or dead supply, board, cpu, memory, hard drive, video card, sound card. You may see a newer supply work on an old system like that but don't expect any old supply to run any recent build.
The questions here would be when was the last time it actually ran?, when did it stop and were you running any particular programs at the time? or was it sitting idle to simply switch off on it's own?, or refused to start up at all one day? How long was run daily if even run on any daily basis? could be another question to ask.
All that is rather pointless however since you would better off simply selling or swapping it off as a parts puppy unless you were able to replace the item that failed and run it for how long before... ?