Good catch there Trotter, I didn't check his Motherboard/CPU compatibility.
Phenom IIX2 550 (HDZ550WFK2DGI),3.1GHz,80W,rev.C2,SocketAM3,Dual-Core 1.00G
Phenom IIX2 550( HDX550WFK2DGM),3.1GHz,512KB,rev.C3,80W,SocketAM3 1.00G
So if he has the 1.00G Revision of that motherboard, yes, it CAN support AM3 CPUs with the 602 BIOS, and an AM3 CPU C3 revision with BIOS 1105.
The full CPU Support list for his motherboard may be found here.
Also, I'd rather have a Phenom II than an Athlon II if I were a gamer (The Phenoms destroy the Athlons for gaming.) and my guess is that he's a gamer because he has a 4870, and not some budget card.