HelP. Do I have a motherboard problem?

I replaced the original hard drive on my compaq presario s4020wm because it kept freezing on boot up and I thought the hard drive's boot sector was damaged.

I orignally had xp on the computer. The old hard drive is no longer on the computer and the new hard drive is connected just as the original hard drive was connected, but I still couldn't get past the screen with the options: press enter to setup xp, r to repair or f3 to quit.

I set it up on a second computer using the correct product key for computer #1. I was able to set up winxp. When I placed the new hard drive back in computer #1, I got the error message that my computer did not shut down properly and the computer would only boot up in safe mode. So since the hard drive wasn't the problem, what else could it be?

HelP. Do I have a motherboard problem?antivirus programs

Motherboard BIOS settings. Has a conflict!

Check around for a BIOS update.

HelP. Do I have a motherboard problem?computer protection

Check these links for installing a hard drive on another motherboard
In the case of installing windows on another PC and then attempting to boot on this one, that is unlikely to work unless the machines have identical hardware. It could be a memory issue or an overheating issue. If you have more than one stick of RAM, try installing windows with only one stick installed. I would reccomend checking all fans for functionality and then try testing the RAM. Additionally, you may want to check your BIOS to ensure that all of your hardware is being detected properly.
Could be your RAM as I had a similar problem. Look for memdiag on the internet which will test your ram from floppy.

There could be a host of other things causing your problems but I am not entirley convinced the hard drive was not the problem. You can only swap hard drives like that if the computers are identical. Even then Windows will lock down on you since three or more devices have changed in a six month period.
you can't install windows xp in one computer and then take out the hard drive to put in another, it will cause errors unless the machines are same brand same model, so, put your new hard drive, try to enter the option of 'repair' and put the windows xp cd inside the drive.. it will reinstall the drivers for your pc, must work.. good luck