Hello forum users.

About 1 week ago, I bought a brand new 500GB Western Digital external hard drive. I bought it as I intended to use it as a backup and file transfer drive.

I made 2 partitions, one for backing up my Macbook's (2008, 2GB RAM) contents, and a FAT32 partition for transfers and file storage.

Now, am I right for making a FAT32 partition so that I can transfer files between Mac and Windows computers?

I gave my external to my friend to put music on it (he has windows, so he put music on the FAT32 partition). When I got it back today and had a look, my backup partition was fine. But my FAT32 partition was not mounting. Disk Utility recognizes that it exists (but with a different name, "disk1s3"), but no matter how much I try, it will not mount.
By the way, the FAT32 partition is 140GB, and has about 120GB of music on it. I heard somewhere that Mac OS won't mount a FAT32 drive that is above 128GB. Is that true, or do I have a different problem?
First of all, has the files my friend put on been lost?
Secondly, how do I get this drive back to my desktop, and if I can will the files be lost?
Thirdly, how do these things happen?

Please help me.