How to Detect Harddisk?

I’m using Pentium MMX 200MHz, I am using a 4GB Harddisk (Quantum) and I would like to add another 10GB Quantum lct10 harddisk. But when I run bios setup, it only detect as 8GB. How am I suppose to get the another 2GB back since my PC is not supporting more than 8GB harddisk?