Hi,
This is the HP advice to start their Recovery Process in XP machines:
"Just after the first screen appears (the logo screen), press the F10 key repeatedly until a recovery menu appears"
http://h10025.www1.hp.com/ewfrf/wc/document?cc=au&lc=en&docname=bph07145#N296
Did you follow HP's exact instructions?
If you did, please explain what problems led to you wanting to reinstall the Operating System.
It may not be only be a Software problem; but may involve Hardware problems as well.
Cheers.
Edit: FYI from HP:
NOTE:HP computers that ship with Microsoft Windows XP do not come with recovery CDs. Instead, they use a hidden space (partition) on the hard drive to store the recovery information. The use of a separate partition provides a convenient process that eliminates the use of recovery discs that may be lost or scratched. A system recovery from the hard drive may not be possible in some circumstances. Your computer may contain Recovery Disc Creation software. Recovery discs for Windows XP are available from HP for a minimal cost. See Obtaining Recovery Discs for ordering information.