Try the instructions here:
http://www.msfn.org/board/topic/51140-integration-of-nvidias-nforce-raid-and-ahci-drivers/page__p__356029
The short ("fast & dirty install") instructions usually work well but if you are having problems then use the longer detailed instructions which don't have any of the shortcuts. This is all about identifying the AHCI .inf files from nVidia so the nlite install pushes them at the right stage of the XP install. Note the setup differs between 32 & 64-bit versions.
Otherwise leew has the pragmatic solution - you need to be sure the USB FDD is supported in your BIOS though.