Is there any way you could be able to ghost (aka, image) the hard drive? I'm thinking that you may be able to get away with imaging the 14" hard drive and throwing it into the 15". I know from experience if you happen to actually be downgrading hardware (P4 to P3 for example), Windows 2000 should not be able to tell the difference (I've done it before, P4 to P3, both Dell Optiplex).
Also could you take some more pics of the mobo? Just to get an idea of what connectors you have to work with
Xb0x3r