How to format large external Hard Drive to FAT32

I have a 500GB external Hard Drive that I need to use at home with my Windows 7 PC and at school where I use a Mac.

I know NTFS is for Windows only and I know FAT32 works on both Windows and Mac.

However I have been unable to format my external hard drvie to FAT32. Only to exFAT which doesnt work on Windows.

I have tried in CMD using the format fs=FAT32 quick but it told be my hard drive is too big.

Any ideas?

Thanks

Nevermind lol I used a program called guiformat.exe - worked like a charm. I decided to leave this post up in case it helps someone else.