Dimensions 4440 w/Dell M991 on NVIDIA GeFORCE 3Ti 200 on Windows XP

I have been trying in vain to install a second monitor. It's an old GVC M1488. I initially tried with two video cards (1st an ATI Mach 32, which was reported by the Device Manager : This device is unable to start, and 2nd with a Diamond S3, with just as little luck). I also on forum advice tried a DVIVGA adapter (which was later discovered not to be suported).

Has anybody got any ideas of why either the Video cards don't work or how I can go about sorting this out. Have tried the usual troubleshooting route, but as usual is completely hopeless.

Regards

Deborah