Pavilion 8575c Won't Start Up

I posted a message a while back about a startup problem after
replacing the CPU cooling fan on my friend's Pavilion 8575c and I'm
looking for more opinions on what might have gone wrong. All I did was
clean out the dust inside the chassis with compressed air and replace
the old CPU cooling fan with a new one with an identical model number.
After that, the computer wouldn't shut down properly and I'd have to
cut the power to turn it off. It would then start up automatically
when I plugged it back in without my even touching the power button.
The power supply fan would turn on but the CPU fan wouldn't, and the
hard drive wouldn't boot up either. No beep, no display, nothing. The
power light would stay on, but the hard drive light would go out after
about 10 seconds. It also wouldn't shut down when I pressed the power
button, so I'd have to cut the power to turn it off. I replaced the
new CPU fan with the old one and it still has the same problems. If I
take out the CMOS battery for a few seconds, that solves the problem
of the computer starting up automatically when I plug it in, but once
it powers up (without booting up), I have to cut the power again to
shut it down and then remove the battery once again to stop it from
starting up when I plug it back in. I don't know what the hell
happened. All I did was replace the CPU fan. I'm worried that the new
fan fried the motherboard somehow. Although the model numbers of the
two fans are identical, the new one only had two wires whereas the old
one had three. Someone replied to my last post and told me that the
new one doesn't have a trachometer and that might account for the
problem. But I put the old fan back in and I'm still having the same
problems. Someone suggested the power supply might have gone bad, but
that seems like too odd a coincidence since it showed no signs of
trouble before I replaced the CPU fan. The power supply fan does turn
on and I can open the DVD and CD-RW trays. Obviously the CPU fan
replacement screwed something up. Any ideas on what happened and what
I can do to fix it?