If the hard disk in the laptop is the SATA hard disk (quite likely) either find the driver on a diskette and give that to the XP installer when it asks for a RAID driver, or find a Windows XP SP2 CD (not the original version or SP1).

Are you VERY sure you've downloaded all XP drivers for this notebook. HP drivers for XP for laptops are notoriously difficult to find, if available at all.

The best advice I can give to you if you want to get rid of Windows Vista is to buy Windows 7 and go forward. Don't go backward to XP.