Computer beeps on start up? help!

i installed a 4400+ duo core from a 3500+ and when i started it up and would just beep and shut off the first time. i tried again and it started up fine. it went to the desktop like normal and my computer read it fine. then it said my computer needed to be restarted for some reason so i clicked yes.

I then opened bios to make sure it read it fine and it did and then i exited and now it wont start up and all i get are beeps. i tried resetting the ram, video card, replugging in the HDD.

What i found odd is that the fan plug for the new one had 4 holes to be connected to the motherboard. My old one had 3 holes. But it fit just fine and spun just fine.

help?!

Check ur ram it might be loose reinstall it

this may sound like a dumb question but how can i find that out? i know my bios is version 3.0? but how do i know if its compatible?

I just tried checking HP's support site. There does not seem to be any new BIOS available for download.

What is confusion me somehow, is that someone who has the same machine has a version 6,0 BIOS. But that may be due to motherboard differences. Check this: http://www.bleepingcomputer.com/forums/topic146070.html if you are curious.

Sorry I couldn't be more helpful.