Question : Problem: XP Pro - Dell Precision 340 - Installed USB 2.0 pci card and computer completly locks when I move over 200 megs to Netdisk Mini.

Locks = nothing does anything. Have to hold power button down until powers off.
This happened once when I was not moving data, but I can make it do it anytime by moving over 200 megs of files to the external hd. The speeds are good until the lockup. I have SP 1. The computer has been up for an hour now without locking. Bandwidth reserved is 10%. I first used native XP driver then downloaded driver from site and same thing happened.

Answer : Problem: XP Pro - Dell Precision 340 - Installed USB 2.0 pci card and computer completly locks when I move over 200 megs to Netdisk Mini.

I would test that PCI USB card on another machine to confirm whether it is working or not.  I would also try a different cable, in case this one is not damaged.