installed new power supply that died after 12 hours

I have an HP Media Center PC whose original power supply had died. I purchased a generic one (as in not the exact one but had the same pins, etc), installed it and got the computer to work fine last night and this morning. Just about an hour ago the computer froze and got a blue screen error message saying to restart. I turned off the computer but now it won’t turn back on or even make any noise. Any thoughts?