[PoWerZ]

I have kind a big problem,
I can open alot of accounts with a 1 nick.

it means fexist(filename) - doesn't reckon same nick
with different capital letters as same value.
Example:
I'm an admin and my nickname of the account is PoWerZ.
but someone can still open same account but with different of capital letters like.
powerz or poWerZ.

i want to ignore the problem,but fexist function doesn't take it as same :S
any sulotions?