I have the same problem with My wow account I get a hard lockup with a odd buzzing noise, and have to either reset the PC or hold down power button till it powers down.
I have all updated drivers, done the file deletion asked by Blizzard, actually all steps they guild you through. My specs are these.
XP Pro SP3
AMD Athlon 1.75 ghz
768MB of RAM
Nvidia Geforce 7300 GT
Sound Blaster Live 5.1
Hope this issue can be fixed.
Mine does the exact same thing, though it will restart on it's own, when it does it goes to a blue screen saying "there was a problem and windows had to restart" it then goes through the restart process and in doing so gives me a "CPU overtemp" warning page that tells me to hit F1 to continue, I do so and have no issue unless I play wow again.
Windows 7 64 bit home premium
AMD Phenom II 1090 3.2
4 gigs ram
AMD Radeon HD 6700 Series graphics card
VIA High Definition Audio
Motherboard: ASUS Crosshair IV Formula (AM3)