Go to the www.hp.com site and look up Compaq Armada 1750. I would install all new drivers if it were my machine. The driver you likely need is the ATI Rage LT Pro. But there are 33 models of the Armada 1750... so use the lable on the back of the machine.
Upgrade BIOS, Firmware, OS Enhancements, Intervideo, and Smart Card as well, if you have never done so.