Kazaa low bandwidth on new HDD

I have a client with a 30GB HDD running XP Home, with a Netgear DM602, getting bandwidth of 456 on Kazaa on some files.

I have replaced the 30GB HDD with a new 185GB HDD, then done nothing but a new install of XP Home, the DM602 and Kazaa but only get max bandwidth of 68, sometimes 108.

If I put the old 30GB HDD back in it goes up again to 456.

I have updated the BIOS and firmware on the DM602 to no avail. The settings on the DM602 are exactly the same for both HDDs.

Any clues??