Thanks TRoss.
Whilst it does detect the WD drive, I'll use the official support tool from WD to do the WD drive. The Seagate one set it perfectly for the Seagate drive, so i figured it might be a universal tool and would save me burning another CD
Quite a handy feature, despite most people probably thinking that it's crazy, "why would you want to set the drive size smaller?" - a perfect use for small business machines where capacity isn't a huge requirement, but performance is. Afterall, the first 40GB of a drives platter(s) is incredibly fast. Later on when the drive is decommissioned, woop - remove the lba setting and you've got a handy 250GB drive!