[Burgerboy2k9]

Hi there, I have 2 computers, one of which can only boot from hard drive nothing else(NCR 7454), so in order for me to install an OS i have been installing DOS and precopying all files onto the harddrive elsewhere.
The hard drive boots up fine on my second computer(sony laptop) but when i try the hard drive in my NCR it comes up with invalid system disk, the bios is all set up correctly and it is recognising the hard drive is there etc...
It worked a few months ago with the same procedure, done on a different laptop, but i can't understand why it doesn't anymore...

Any ideas?