hard drive problem?

I have a Western Digital 160GB IDE (i know it sux) hard drive for my computer. I'm not sure if it's the hard drive's problem or not. But my computer randomly restarts. My temps are at 40C idle and i don't know the load temp. At first I thought my comp restarted under load, but it also restarts when I am surfing on the internet and using aim. I was thinking it was the hard drive because a while back i was doing some maintainence in my case when all of the sudden the hard drive started spinning and making grinding sounds.
I have another Western Digital 120GB IDE hard drive. Can I just put the in my comp in addition to the 160GB drive and copy all my folders over? Or will that cause problems with the shortcuts, etc.. Is there some way that I can copy my 160gb onto my 120gb hd?

Download Data Lifeguard Tools and use the "Disk Copy" feature to image the one hard drive to the other. Then remove the old one and boot with the 120GB drive.

As far as your rebooting promblem, I'd consider the PSU or your memory as the culprit of that. But you're overclocking and you're system isn't stable so you've got some troubleshooting to do. Either your CPU or memory may be running past it's limits as well. Put your settings to stock and see if you get random restarts with your 160GB HDD. My bet is you don't.