Dimension 2100,boot error, trys to boot from A

I am working on a Dell dimension 2100 computer that had a failing hard drive in it,It originaly came up with a BSOD saying UNMOUNTABLE_VOLUME, but we were able to fix that, however it came back after a reboot, leading us to beleive that the drive was failing. Using norton ghost we ghosted the contents of the drive onto a brand new 80Gig drive and tried to boot from that, however it always says "Invalad System disk" "insert disk into drive A" on boot, even when the A drive is turned off in the BIOS as well as Physicly taken out of the computer. I ran the Dell 32bit daignostics from this site (on 5 floppys no less) and it found that the only thing "wrong" with the computer was that the 'secconds' regester in the Real Time Clock was updating too slow, this would lead to bad time keeping but should not prevent booting. We checked the dell Diagnostic lights on the back and they show up like this

0 0 0 X
A B C D 0=Green X=Yellow

according to the documentation, the description for this pattern is "other", which doesnt really help much. all of this leads to the conclusion that something is wrong, but I dont know quite what it is....
I hope someone here has some insite..