i inherited a 1.6GHz Power Mac G5 and decided to make use of it as a server of sorts. Home network file serving, light FTP, nothing too crazy.

I received the machine as bone stock as the day it was born. 1.6GHz single-cpu, 256MB RAM, 80GB hard drive, and OS X 10.3.9. My brother's data was still on the 80GB original hard drive, so I simply replaced it with a Western Digital 750GB SATA drive. While I was at it, I also swapped the two 128MB memory modules for a couple 1GB sticks and upgraded the "SuperDrive."

The new 750GB was christened with a new install of Leopard and that's where things went south. Any amount of normal use will eventually result in the mouse/video freezing. If the computer is sitting serving files, it can seemingly run forever. Once I start doing something like web browsing on it, the computer will always crash to the point I have to hold the power button to shut it down.

At first I thought Firefox 2.0.0.9 was to blame, but then it froze while working in Safari and once while transitioning from one Spaces desktop to another.

My initial though was that I have bad RAM. However, I was transferring data from a USB hard drive during one of the freezes and, although the screen was stuck, the transfer seemed to still be going along fine. Could it be the video card is somehow to blame? It's the stock 64MB nVidia model that seem to work fine in the older OS.

This is my first major leap into Apple computing, so I have to admit I'm a little clumsy when it comes to moving around the OS. I can't really find anything that can diagnose my problem. Are there any utilities available in the OS, or something I can download? Any known compatibility issues with something I've installed? Should I attempt to reinstall the OS? Any ideas?

Thanks.