Okay, so I had XP installed on a Seagate 200gb drive and installed a WD5000AAKS (500gb), I had just installed the drive and some unbeknown reason I installed Acronis Partition Manager, (instead of the usual partition magic that i normally use)and this has made my WD unrecognisable and unreadable. (it recognised it at the start but after a reboot it now doesnt)

By that I mean, when it loads up from Bios, instead of the name of the drive everywhere I just see a blank space and no additionally information can be found about it in BIOS, of course it doesn't show up in windows or anywhere else.

The problem with a completely unrecognisable 500gb hard drive remains though, I can't auto detect to fix it. I've tried plugging it in and out, swapping machines, changing SATA cords etc. I've tried a smorgasbord of DOS (only one recognised it as a drive with no other info except a size of 0gb) and Windows hard drive recovery programs, all the rest either crash or fail to recognise the disk, and specifically I've tried everything I can find on the WD site. Also, I'm more or less positive it isn't a mechanical issue, it was working perfectly until the day I installed this insidious partitioning program, not to mention it was only about 2-3 days old. Could it be this program somehow mucked with the firmware on my hard drive? If so ... is there any possible way to fix it without sending it off to hard drive repairs and forking out a grand?

Perhaps, it's something even simpler because I really find it very difficult to understand how a piece of software can brick a hard drive like that.

Anyway any help/advice would be much appreciated.

The problem is most probably due to deleted firmware. I see the drive is preety costly and so I advice not to fidle with it anymore. Get it to a WD service center, they'll have it fixed. You will get a hard time to convince them its a normal failure. Else, try to download the firmware and see what you can do...