My friend gave me his computer to take a look it. It's a Dell Demention 4600, about 3 years old. When I first tried starting it up, it got hung up on the Windows XP loading page, and never actually got to the desktop. I tried to run it in safe mode, but would get hung up also and never got there. So I pulled the HD out, put in into one of my other computers, and it was in bad shape. I was able to extact most of the files from it, but I decided to put a new HD in the Dell to see if that was the problem. After putting in the new HD and formatting it with XP Pro, there was still a hangup at the loading screen and the progress bar was moving very choppy like, but eventually (1-1.5 min. later) it would reach the desktop. Then, as I started navigating through windows, I realized it was very slow going. So I opened up the task manager, and the CPU was pegged at 100% with explorer.exe at around 70% of it. It would drop off a little bit occassionaly, but usually it's pegged out - even with no applications running whatsoever. I disabled the modem and sound card to see if those were causing the problem, but no dice. The HD is brand new, and I haven't connected it to the internet, so spyware/malware isn't an issue. I haven't loaded any programs on it. I'm thinking it's got to be a hardware problem.
So, any suggestions or procedures I should do to figure out what's going on? Does it sound like a CPU or motherboard issue? Any other hardware?
Thanks for the help!