I have the original fat 60GB PS3 (the one with the backwards capability). I brought Western Digital Scorpio WD3200BEVT 320GB HDD hoping to upgrade my space as my 60GB has gone lol. I put in my PS3 and got "Correct hard disk not found" (or something along those lines).. a long story short - I checked all the forums, and even called Playstation, and after hours and hours came to realise, that the simple fact is, this HDD is NOT compatible with the Original Fat PS3 60GB (playstation don't know why, just something to do with the system software) - Play.com were excellent, returned the item and got a refund within a week - I then brought the Samsung Spinpoint 640GB for 8 quid more (but as it's double the memory, it's worth it) and that worked perfectly, really was a simple as it is suppose to be. Put it in the PS3, then the playstation formatted it etc and it was done in 2minutes (restoring my backed up files took a few hours obviously).
To sum up - If you have the Original 60GB Fat PS3 (backwards capability) that come out when PS3 was released then DO NOT get any Western Digital HDD, the PS3 won't recognise it - instead you need to get the Samsung Spinpoint HD and that WILL WORK.
Hope this helps others not to go through what I did.