Ok, I dont know what happen, usually I think I keep my computer pretty protected, I think this may be a hardware issue and not a virus or spyware issue. I came and turned on my computer one morning and it would get to the windows boot up screen then i would see this little pixelated bar at the bottom fill up(but sometimes its just a blank screen) and the computer restarts and I have to reformat AGAIN =( Well I thought maybe it was the harddrive so I bought a new one and im using it now but I have restarted a few times with it (sometimes the problem doesnt happen right after the first few restarts so im still here) but the last time I restarted I saw that pixelated bar fill up but the computer still booted up (thank GOD) but im afraid if i restart again it will happen. Is there anyway I can keep this from happening again because im really tired of reinstalling everything, i think this is the 3rd or 4th time and when you have to redownload, reinstall it is really a pain, so please help me! Maybe I could make something that will make the computer boot up fine, a disc or something, im not sure, you guys are smarter than me. Please help!

Edit: My computer specs by the way if you guys need to know... Asus mother board A7n8X-E Deluxe, Radeon 9800 pro graphics card AGP, AMD Athlon xp 2800, 1gb dual channel ddr 400 ram, cd-rw 48x or something drive, 160gb UATA hard drive 8mb cache 7200 rpm (same specs before when it crashed but it was SATA and 80mb) 480W Demon power supply, (I know the airflow is good so I dont think thats a problem)

Just to clarify:

With the new drive you're booting ok, except the "pixelated bar"?

Really need to get error messages:

Try turning off the feature that instructs XP to autostart on system
failure. Right click on My Computer and select Properties->Advanced
Tab->Startup & Recovery section->Settings button->uncheck "Automatically
restart" Apply. This will give you a blue screen with info on it and you
will have to manually restart the computer. The info might give you an idea
whether or not the problem is hardware or software related.

Also look in the Event Viewer for Red X errors under System & also Application tabs:
Start > Run > (type in) eventvwr.msc

Post back any errors that relate to the boot time