this is typical, as your primary partition will be a small fat32 partition with the recovery utilities in the event of a crash
but first of do the following
make a recovery ( for vista ) disk, somewhere in the HP utilities will be the tools for doing that
once the DVDs are made, this in case you ever ( doubt it ) go back to Vista
secure all the driver needed for XP, typically it's the chipset, the SATA driver, the LAN driver, Video driver, Audio Driver and so on, despite HP stance on no more XP support, you still can find the drivers, as HP does not make their own hardware, so you might have to go direct to the hardware website for drivers, sometimes you get lucky and can find zipped up driver packed all ready fro your laptop uploaded to rapidshare or other file sharing sites, I found my drivers partially in this manner and by going to Toshiba of Canada, again Goggle is your best friend
make sure you BIOS is set to boot from the CD and to not boot to any secondary device ( HD0 or USB )
hunt down program called killdisk, this will positively kill the partitions on your laptop, it's free and it should be a small bootable cd DOS image, burn and boot to it
next
I'll assume your XP disk is bootable
as if it's not
then you not going to be able to do anything
as the XP disk must be bootable ( OEM or Retail ) to install XP over Vista
once you got the XP CD installer booted the rest should be easy from there, though on HP you might need to adjust a setting in the bios for "Native SATA" drive that
might to be disabled in order for XP to see the drives normally
though when I did the conversion on my Toshiba laptop ( and I do not consider it a downgrade but an upgrade ) i used a customer version of XP Sp3 which included SATA drivers so it booted seeing the SATA drives ( 2 in my laptop )
once done you see how fast XP will be ( especially if you use Nlite on XP and strip down the unnecessary processes or hunt down the eXperience post install service scripts which will shut down and install unnecessary services
BTW you biggest issue will be the audio
as was for my toshiba
here are you 2 key issues---
- Atheros AR5007 802.11b/g WiFi Adapter.
- Conexant High Definition SmartAudio 221.
Atheros Ar5007:
http://www.atheros.cz/download.php?atheros=AR5006EG&system=1
MS UAA Hotfix(required with a reboot before Conexant):
http://www.mediafire.com/?4ben9zlesng
Conexant SmartAudio 221:
http://www.mediafire.com/?dg0cmmkm4y4
READ Carefully>>.Unzip to a folder.Run installer.if it errors use Device Manager.
From Device Manager,right click "Audio Device on HD",choose Update driver,
No to connect,
Install from a list or specific location,
Select Don't Search, I will choose the driver to install,
For the Hardware Type select 'Show All Devices'
Remove the check from "Show Compatible Hardware" and click on "Have Disk".
Next...browse to the unzipped folder and choose the "WiSVHe5.inf".
Ignore XP when it complains.
Reboot.
XP SP 2:
http://www.microsoft.com/downloads/details.aspx?FamilyID=049C9DBE-3B8E-4F30-8245-9E368D3CDB5A&displaylang=en