New Build Problem: XP won't install, but Ubuntu runs perfectly

So I recently purchased and assembled myself a nice new rig with the following hardware:

AMD A8-3850 Llano 2.9GHz Socket FM1 100W Quad-Core Desktop APU
ASRock A75M FM1 AMD A75 (Hudson D3) HDMI SATA 6Gb/s USB 3.0 Micro ATX AMD Motherboard
Antec EarthWatts Green EA-380D Green 380W Continuous power ATX12V v2.3 / EPS12V 80 PLUS BRONZE Certified Active PFC Power Supply
Kingston 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory
APEX TX-381-C Black Steel Micro ATX Tower Computer Case
Western Digital Caviar Blue WD5000AAKX 500GB 7200 RPM 16MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive

I am quite pleased with the result. I first installed Ubuntu 11.04 from USB, and in runs perfectly. The graphics are quite excellent now that I've installed the proper ATI driver.

So I figured I'd put windoze on it so I could dual-boot. In my experience I'd have to reinstall linux afterwards, which was fine. I couldn't find my Win7 disk, so I found my old (legit) XP key, downloaded a reputable-looking ISO from piratebay, and used WinToFlash to set up my USB key as an installer. (I'm too cheap to buy an optical drive.)

No good - it said hal.dll was corrupted. After some more tinkering I got it to bluescreen during install instead (STOP 0x0000007B). So, I tried using usb_multiboot_10 instead using these instructions.

Nothing but STOP 0x0000007B some twenty seconds into the install. So I checked out what the probable causes of this were.

Hard drive settings in BIOS: not the problem. Mine were set as follows: SATA Controller: Enabled, SATA Mode: IDE, and SATA Combined Mode: Enabled.
Driver issues: probably not the problem. I disabled everything I reasonably could in the BIOS (HD Audio, infrared controllers, some odd audio features of the mobo) with no change.
Memory issues: Since I've witnessed Ubuntu using more than 4GB at once, I'm assuming that both sticks are ok enough to at least allow an install.

Does anyone have any further suggestions? Did Ubuntu possibly do something odd with the partition or boot tables that windoze doesn't understand? Is this likely to still be an issue when I finally find my Win7 disk?

Any suggestions are greatly appreciated - thanks!

find a proper xp SP2 disk

I installed it fine into a virtual machine...but yeah I should probably find a real disk somewhere.