Its a X48
I had no problems with it on an X48 , but it ran XP Pro and Norton Corporate Edition. Put 7 on the sytem , but had moved the power supply so have no idea if it would have worked or not.
My P55 used 7 Ult. 64b and no AV.
Currently have it hooked to an X58 with 7 Ult., again no AV , no problems.