Case-Sensitive Usernames

I was wondering if anyone knows if it is possible to make Usernames in W2k case-sensitive and how? I am looking into using W2k Radius Server and need the usernames to be case-sensitive. I have looked all over the internet and Microsoft’s site and can only find reference to passwords being case-sensitive. If this is not possible, are there any recommendations for Radius software?? Any help will be greatly appreciated.