Large Disks lose loads of diskspace

[duncan]

I installed 2 new 200gb harddrives lately. Both show up in bios as 200gb, on 
boot they are shown as 190gb (probably the 1000->1024 conversion), but when I 
create a filesystem they are only 180gb.
Now, I can live with a 20gb loss, but when I check the disks free space, they 
have only 166gb free with 0 gb used. Could be me, but I find 34gb a bit 
excessive. I hope anyone has a clue as to what I'm doing wrong.

Hope someone knows what is going on.

Regards, duncan.