How to install win xp on Vista ???

And need to install the drivers for it by pressing the F6 at the very first Blue Screen on the XP setup Installer. Now the problem is that the XP installer looks directly to the A Drive to find the files necessary to load the SATA drivers so you'll need to look on the Compaq Web Site for XP Drivers for the SATA HDD or M'Board Chip Set Drivers and then copy the SATA Drivers to the Root of what passes as an A Drive on your system.

Of you could try following the instructions here to Slipstream a XP Install copy that includes the SATA Drivers. I'm not sure how well this works as I've never tried doing it but it would be the fastest option if you don't have the ability to access an A Drive