You did NOT buy a Pentium 4 in 1996. I promise
![;) ;)]()
You bought a Pentium with MMX support in 96 maybe or you bought it in 2006 with a P4.
If it has a 350w power supply in it then pretty much any cheap 350w power supply should work to replace it. I normally would never recommend a cheap PSU but that is an old cheap computer to begin with and not worth investing much money in. Go to newegg.com and look for the cheapest one you can find with the same specs as the sticker on the old one.