They're compatible with about every PC desktop, but some desktops aren't compatible with all keyboards. Intel chipsets seem to handle about everything, but VIA's don't, maybe because of bad BIOS programming (Asus boards have worked when FICs with the same south bridge haven't). VIA's south bridge will also fail AMI's old keyboard diagnostic.
If you're going to buy a genuine IBM/Lexmark 101 keyboard, the kind that clicks, try to get the type with the 3-chip controller inside it because it seems to be more compatible than the 2-chip versions. Later IBM keyboards are by NMB (no click), but compatibility varies by version, just as it does for NMB branded products.