Server setting -- Character encoding

I have a character encoding issue on one of my servers. The files and db`s are exactly the same on both servers. On one of the server the characters are showing as its supposed to, but not on the other one. That makes me believe there is a server settings which causes the issue.

I dont want any changes to the source-code, nor to the db. I will provide access to both servers. I have tried to sort this out myself, but its frustrating when Im not getting anywhere.

You must be familiar with iis and php.

Environment:
Windows server 2008 r2, php 5.3, iis 7.5, mysql