Windows 7 Connecting through shared WEP security

I have a MacBook Pro that is connected to the internet through an ethernet cord. I have a Vista and an XP (seperate computers) both accessing the internet via wi-fi through the Apple. For some reason, I keep getting a message that Windows 7 cannot connect through the shared WEP security settings. If I turn off the security, it works great. Because I am opening the internet connection through a computer, I want to keep it under a security code.

Anyone else had this issue or know how to fix it? I can't even send the feedback to Microsoft to tell them about their issue, lol. BTW, I have Win7 32bit.

Thanks