I've found most of the GPUs will still work, they just won't produce an image before Windows is loaded. A problem when building fresh, but not so much upgrading.
Worth it to keep an old PCIe graphics card around for troubleshooting.
Worst case, time to upgrade everything. 1st gen i7 is pretty dated. Most of your entry level i3 are a match for even the hex cores in throughput. Single thread performance is almost double. Any i5 or Ryzen hex core is going to be a vast improvement and that would not be that expensive.