Vista Special Character Conversion

I have developed an ActiveX control in Visual C++ and in it i create a string
using delimiter "æ". This String is than returned to browser which uses Java
Script to post it to some other page. This thing works fine with IE 7.0 and
IE6.0 on windows XP but when i run it on IE7.0 using windows vista my special
character is converted to "Ùˆ" which creates problem. Can any one help me in
this regard. Why Vista is behaving like that?

Thanks in Advance.