How to install XP over Vista (BIOS can't disable... I have tried many things to install XP over

Question

I have tried many things to install XP over vista but no success! I always get blue screen of death. I installed XP on same HD but in other computer and it worked just fine but as soon as I put it back in original notebook i got same blue screen on XP sturtup.
HP F.05 BIOS can't disable native SATA mode for HD. I want to flash BIOS but I don't know which should I use and which version is suported by motherboard, and I have never done it before as well.
HP pavilion dv5-1002nr
AMD Turion X2 Dual-Core Mobile RM-70, 2.0 Ghz
3 GB RAM
250 GB HD WDC WD 25 00BEVS-60UST0 SCSI
Motherboard 30F2 Hewlett-Packard
BIOS name Default system BIOS
SMBIOS Version F.05
OS Microsoft Windows Vista Home Premium 32 bit Version 6.0.6001

i have a hp laptop. dv4-1138tx.it is already built in with windows vista.but i would like to downgrade it with windows xp.i have tried ur method of removing the battery and the ram sticks.but still it is not working.is there any other options for me to try out next?thankx.