Hi all. A quick forum search didn't turn up any previous threads with obviously same problem as mine so here goes:
I'm running a Gateway that's about 5 years old, Pentium II ~450mhz, 1Gb RAM, Windows XP SP2. Recently the power supply died and I had to resort to a replacement part that was not exactly identical to the failed part as this part is no longer available anywhere. About a month later now my computer has started acting funny. Pushing the power button does gets power to machine but it doesn't always boot. Usually boots after 2-3 attempts. (Have to power down by holding in power button in between attempts.) Seems to be getting worse. Most times the Gateway BIOS screen appears and then goes black. Occasionally brings up blinking white cursor on black screen after that and then goes black. Rarely brings up cursor then Windows boot screen then goes black. And then finally, sometimes it goes through all those and then brings up the blue Windows screen and I know it's going to work.

Recent scans by Spybot and Sophos AV did not return any malware. Suggestions? Is this hardware or software related? Thanks.