Wait wait...you need to do a successful CHKDSK first on the volume you are attempting to boot into...!
UNMOUNTABLE_BOOT_VOLUME is almost always caused by damaged sectors on the Hard Drive. You should always perform a CHKDSK first before anything else.
cannot be found because you aren't booting into the recovery console using the Windows XP Setup Disc (which is where the file AUTOCHK.EXE can be found), meaning the vital file needed to do a CHKDSK successfully is not available.
You need to manually locate the AUTOCHK.EXE
file in order to do a successful CHKDSK. You can check to see if there is a copy on your PC, or just simply get hold of it. I've taken the liberty of obtaining the file:
Simply click on the link above to download it, save it onto a floppy disk (it is only 500KB or so). Boot into recovery using your floppy disks, perform a CHKDSK x: /R
and when prompted to, insert the floppy disk containing the AUTOCHK.EXE file and enter the location. Then let your PC do the rest...!