Many of these machines only respond to the PS2 keyboard for the cancel to work.
I've seen chkdsk take a very long time on big drives. You didn't tell how long you gave it. In fact, not a word about the machine here.
Try http://www.computing.net/answers/windows-xp/disable-chkdsk-at-startup/36357.html too.
I have followed the instructions on this site -
ie used Run > chkntfs /x c:
but this hasn't stopped chkdsk going on and on at start up.