Some versions of Vista will only do a full install. In any case, it is so buggered up now, probably a reinstall of the appropriate OS will be required. Your old Windows install MAY be in that folder (what is inside) but the booting instructions, etc. will be for Vista.
Are you the original purchaser of that machine? If so, HP may be willing to send you a restore CD. You didn't make backup discs when the machine was new?