Ok, i have a similar Toshiba, i did not find any options in the BIOS like i mentioned... Do you still have windows installed on it (vista?) We can identify the right chipset, download the INF drivers and either include it on a CD or use a USB Floppy.
Intel® Chipsets - Identifying your Intel® chipset
This has chipset drivers:
Download Search Results
Once you have the right chipset drivers, you can include them in the WinXP install CD. I've attached a .zip file with the instructions within it. You should have to drop the drivers in 2 directories (\i386 and \$OEM$\$1\DRIVERS\SATA) then follow the rest of the instruction on burning the CD.
The easy way of course would be a USB floppy drive.
I haven't tried this method myself since i'm actually configuring this for Toshiba for someone else, but when i'm done i'll give it a go. Let me know if you're having any problems or if this works out for you. I'll try to post my results soon.