Problem when erasing external drives
I have an 80 GBs drive that I once formatted (erased) using Disk Utility. Now I have a 2 GBs flash drive that is empty when I open, but it says that 200 MBs are left, so I went to Disk Utility and erased that too, and now it says 2 GBs free. Good. Now when I plug either of these external drives to a Windows system, they never get recognized, they never show up. If I plug either of them on my Mac, they show up and work normally. I have two questions please:
1- Why does this happen?
2- How can I make them work on Windows normally?
White MacBook, iPhone 4, 64GB WiFi iPad, Mac OS X (10.6.3)