Please help me - lost my data drive!

Hi folks,

I need some help here - I have lost access to my data partition on my 500 gb WD drive. This drive has all my programs and data on it, including 100.000 precious photos.

This is the story:

I just bought a new 500g external drive, and wanted to format it. since this drive is going to be used for backup on both PC and Mac, I thought FAT32 might be the best shot - even though I know the limitations of this file system. Since Windows wont let me format a 500gb drive to FAT32, I was adviced to try Partition Magic. So I installed partition magic 8, Vista threw up a compatibility error, which I happily ignored. On first lauch of Partition Magic, it adviced me that my data drive had some bad sectors it could repair for me? Again, I happily clicked on. The drive still worked fine after this.

Only this morning, after botting up, I could see right away that I had no access to my drive anymore.

The first 20gigs of the data drive is set aside for Photoshop Scratch, as a logical drive 'S' this partition is visible and usable - the rest of the 500gigs, are for data and programs, and it is this partition 'J' that I cannot access anymore. I can see the physical drive in Boot setup and Vista disk manager, but any action in disk manager tells me that 'disk manager is not up to date, try a refresh', but ofcourse it doesnt work. If I only could scan the bad partition and try to recover bad sections - but how do I do this when I can't access?

I really dont want to loose my data on there - any help is very much appreciated!