the Recovery Drive for Vista is actually still intact as a separate partition I do not have recovery disks.
I'd be very careful not to wipe out that recovery partition. You should be able to restore the system to its original configuration by hitting F11 during startup, which should start the recovery partition.
Indeed, I think I'd reinstall Vista from the recovery partition if only to create a restore disc on DVD from the recovery partition. That's really what computer buyers are supposed to do; that way, they have a recovery disc, on DVD, in case the hard drive must be replaced or that recovery partition gets deleted or erased.
Once that's done, i.e. creating the DVD recovery disc, then the Win XP installation could be done again.