matthew_sargent, I think this has something to do with 28 bit addressing which means only the first 137GB will be recognised.
Personally I haven't come across the problem but note there are several suggestions around, like:
Use a RAID header as it has 32 bit (64 even) addressing or,
upgrade the BIOS or,
there should be a special IDE controller upgrade on a disk supplied with the HDD.
Best I can do.