Yay for mobo model numbers.
Sapphire PURE Innovation PI-A9RX480
Processor AMD Athlon64 / FX Socket 939
FSB 800 MHz / 1000+ MHz
Chipset ATI RADEON XPRESS 200 (RX480 + SB450)
Memory 4x 184 Pin DDR, Dual Channel DDR266/333/400, up to 4 GB
BIOS AwardBios
Slots 1x PCI-E x16
2x PCI-E x1
2x PCI
HDD Connectivity 2x ATA-133
4x SATA, 2x SATA-II
Networking 10/100/1000 Mbps - Marvell 88E852 via PCI-Express
Ports 8x USB 2.0 (4 on Back Panel)
2x IEEE1394 (1 on Back Panel)
Audio 8 Channel Realtek ALC880 Audio, SPDIF
Form Factor ATX 305 x 244mm
So what we're concerned with is video (Xpress 200, probably not gonna get anywhere with that but you do have an X1050 card if I'm not mistaken) and the sound (ALC880).
In both cases someone's going to have to use the search and hopefully find you some kexts.
You got OS X installed once, you should be able to again. As far as I'm aware the SB450 is supported somewhere.
Hope that helps a bit. Good luck.
