Mark Pilgrim: How to install Windows XP in 5 hours or less:

“”Windows Update has found 39 critical updates and service packs.” Install now.
“Service Pack 1 must be installed separately from other updates.” OK.
Yes, I agree to bend over, grease up, and accept the End User License Agreement.
Wait. Time passes.
Wait. Time passes.
Wait. Time passes. It is getting dark. You are likely to be eaten by a grue.
Reboot.

Thanks to Simon for the heads-up.