Support for Socket AM2+ / AM2 processors: AMD Phenom™ FX / Phenom / Athlon 64 FX / Athlon 64 X2 Dual-Core / Athlon X2 Dual-Core / Athlon 64 / Sempron processor
NVIDIA® GeForce 6100 / nForce 430 or GeForce 6150SE / nForce 430 Chipsets
AMD LIVE!™ Ready
Supports Dual Channel DDR2 1066 with AM2+ CPU, and DDR2 800/667/533 with AM2 CPU, with 4 DIMM slots, maximum capacity up to 16GB
ASRock AM2 Boost: ASRock Patented Technology to boost memory performance up to 12.5%
Integrated NVIDIA® GeForce6-class graphics DX9.0 VGA, Pixel Shader 3.0, Max. shared memory 256MB
1 x PCI Express x16 slot
Untied Overclocking : During Overclocking, FSB enjoys better margin due to fixed PCIE/ PCI Buses
Hybrid Booster - ASRock Safe Overclocking Technology
4 x SATAII 3.0 Gb/s, support RAID (RAID 0, RAID 1, RAID 0+1, RAID 5, JBOD), NCQ, and "Hot Plug" functions
HDMI_SPDIF header, providing SPDIF audio output to HDMI VGA card, allows the system to connect HDMI Digital TV/projector/LCD devices.
7.1 CH Windows® Vista™ Premium Level HD Audio (ALC888 Audio Codec), 10/100 Ethernet LAN
Windows® Vista™ Premium Logo Ready
HD 8CH I/O: 4 ready-to-use USB Ports, HD 7.1 channel audio jacks
This says that you can have up to 16 gigs of installed memory. but again with what squirrelnmoose told you....that you maybe able to install the upgrade but the operating system might not allow you to use it....
What you have is the 32 bit version of Windows XP home (home does not have a 64 bit version)
32bit Windows XP will only allow 3 gigs (some says 4) but I have never been able to get it to use more than 3 gigs.