Hardware limitations come before software limitations.
If the BIOS only sees the HD as 30gig, debian will only see it as 30gig. Reason being, debian asks the BIOS what size the HD is.
I setup a temporary server on an older mobo w/ a 120gig HD. I had to flash the BIOS for it to even recognize the HD. Once I did, it was all downhill.
So... flash the BIOS, then you're good to to.