How to restore a external HDD which isn't formatted properly?

Hello, help!

I tried to format my external HDD 320GB Toshiba and it failed! And, oh no! Windows doesn’t recognize it anymore!

I tried to format it to FAT32 for my new Mac, because I use my HDD’s on PC’s too, so I must use FAT32.

So the format failed, stopped unexpectedly, so the HDD is damaged. How can I fix this? I want to use it for Time Machine.

BTW: When I connect it to Windows, Windows freezes, and when I unplug it, Windows un-freezes…

Davey