From my experience HP machines have a extra partition for drivers, Op system & Utilities - in other words stuff that you can DL from HP's homepage (support&downloads section)
In these cases I have formatted the computer using a WinXP CD & downloaded the drivers and
useful utilities from the homepage.
Just-in-case how to install a fresh Windows copy -
1)Boot from CD, Enter Win XP setup
2)After showing U current partitions delete all and format the new unpatitioned space to NTFS
3)Follow the installation instructions
4)Now you need a few programs on your USB stick - a firewall, an antivirus and the ethernet driver (all of these you have previously copied on your friends computer
)
5)Now its safe to connect to the internet and DL all the other drivers from HP homepage.
Good luck...
P.S. If you prefer more partitions you can create an extra partition for the OS & other stuff with step 2 or afterwards using ie Partition Magic