I've just got a new PC, 80gb SATA hard drive.

I figured I was reasonably knowledgeable about PCs, but I was stumped when I found the PC had 2 x 35gb hard drives.

Drive C is NTFS, 34.5gb
Drive D is FAT32, 35gb

I rang because I couldn't work out how 2 x 35gb drives added up to 80gb.
I was told that was because (a) it is standard practice to install hard drives in smaller amounts, and (b) that "modern PCs" never register up to 80gb hard drive, they will never register more than 70gb total hard drive even though there is allegedly 80gb there.

Now whack my head and call me a dipstick, but is what I have been told right? The reason I upgraded was because the PC I had had 2x40gb hard drives and I wanted a 80gb hard drive with space internally to upgrade with a further 80gb, but with having two hard drives installed, there is little or no space to add further drives internally. The ad definitely says 1 x 80gb hard drive.

The PC spec is here:
ebuyer.com - Desktop PCs, Servers » Home PCs » AMD - Sempron » Product details

Any help a.s.a.p. would be much appreciated.