The more modern the card, the less chance of it working. To be honest, though, the only way to know for sure is to try it. There are two major issues. First, there is the issue of PCIe support. While many cards say they are backwards-compatible to the previous PCIe generations, they really aren't completely. Second, there is the issue of UEFI support. Many modern cards simply expect UEFI support to be present and, in many cases, don't include Legacy BIOS support at all. In many of these really old boards, EFI (the predecessor to UEFI) support is provided, but it not enabled by default. Further, even with EFI enabled, many of these old boards require Legacy OpROM formats. Bottom line, there are some brand new cards that will work in these old boards and three-, four- or even five-year old card that won't.
Sorry I didn't have a better answer,