Dude,
I've done what you suggested, and I still get the error, "The file hidusb.sys is corrupted." I've verified that the cabextract created a file in WINXP_EXTRA called HIDUSB.SYS, and I added the two lines to the tftpconfig.
Do you have any more ideas?
The computer is a Portege M200, and I'm trying to install a volumized (corporate license, from my school) version of WinXP.