It does sound as if they replaced your PCIe video card with an older, simpler PCI card. But if the slot was dead, that's the best that could be done.

Time for a replacement motherboard at least.

First question: Your WinXP-SP2: what kind of license do you have? Was it a separate purchase, or did it come bundled with the hardware (aka. an "OEM edition") ?

If it was bundled with the hardware, odds (99.99%) are that it is also "locked" to that hardware, and cannot be freely transferred to something different. But if you actually purchased (WTF?) a retail copy of WinXP for it, then you likely are free to move it to new hardware (within the next few weeks, anyway, until MicroSoft stops allowing new/replacement activations).

So.. sort that out first. The answer to that question dictates what happens next: choice of hardware.

Cheers