Derek,
Seems like you're having lots of troubles getting your machine up and running!
I am not familiar with Fujitsu's drive testing software, but I think I'll be able to help you with it nonetheless.
First off, you need to have a boot disk that will boot your machine into DOS. You said you got the file from bootdisk already. Have you created a disk with it? Can you boot your Thinkpad with it yet?
Second, once you get that working, then you can move on to trying to use it to test your harddrive.
Thrid, I would recommend also running a set of diagnostic tests on your Thinkpad using yet another disk. This one is called:
PC Doctor diagnostic II diskette.
Fourth, as BillP suggested earlier, you may need to upgrade the BIOS. Only the latest version of the Thinkpad 600X BIOS is fully compatible with XP. To upgrade the BIOS (if necessary), you need a fully charged, functioning battery and yet another floppy disk:
BIOS Update (Diskette) - ThinkPad 600X version 1.11 (ITET55WW)
Fifth, after checking the integrity of your hard drive and your Thinkpad, then I would recommend starting from scratch, using fdisk to delete all partitions on your disk. Then try to install XP again.
Phil.