Installing NT Server 4.0

Hi everyone,
I am installing Win NT 4.0 Server on a 20GB IDE Single HDD.
When i am partioning the same it senses only 8GB instead of 20GB. I tried to boot throu CD , Win95 and Dos6.22, but still i am not able to get 20GB HDD while partioning.

Pl. help me in this regard.

regards,
vivek