ok i definatley had this same problem, not to fear i found out how to fix it.
Ok basically i bought a 80Gb HDD, the ppl put it together and everything worked fine, then one dayu i noticed that the HDD was only displaying 60gb (even though it says 80Gb on the HDD).
I was extremly pissed of. I rang my friend and he suggested he bring over a partitioning program, Next time he was over, he didnt have it.
So i set out on a search all over the internet, none of the trial versions would let me alter anything.
I found this DOS one, me, not knowing that i couldnt run DOS under win XP (WTF was i on??) found that it didnt work, i checked my HDD, and guess what, it was working at 80Gb.
I might still have the program somewhere on my other computer, so if you want it, i'll try find it for you.
Regards,
Ph30nIX..