I'm trying to find the board model number as we speak... I got loads of them, too many to remember which. At least I think it's universal slot (pretty sure), it's been a while...
Will update my post if & when I find something
Edit
Found it!
So, the model number is P4SE/U2, using SIS chipset. Ironically, I don't think I have this board any longer, I think I gave it to someone... (It's been sitting around for ages, doing absolutely nothing)
Also, it would appear that SOME revisions of P4S533-MX also have universal AGP slots, but you need to be careful with those, since the newer revisions only had the "4X" one