If you reformat the drive in another PC you may lose your HP repair partition and its possible that the drive won't work with HP's OEM version of Windows Vista. It would be better to have a retail copy of Vista if you plan to go this route. So before you go that route :
-Try uninstalling Service Pack 1
-Did you check in the BIOS that the optical drive (DVD/CD-R or whatever) is set to boot before the hard disk? If this is not set then the PC looks to the hard drive first, It must be set to boot from the CD drive!
Then try to restore for the CD as follows:
1. Open the disk tray and shut off PC.
2. With PC off load restore CD , close the tray, then power up the PC.
HP system restore stuff here: