how to replace none english characters with english characters

[ehsanix]

please help me how to replace none english characters with english characters.
i mean in forum title
for example i want to replace "?" with "a"
i want this :
http://forum.mysite.com/f-?bca-128.html
to be like this :
http://forum.mysite.com/f-abca-128.html
please help me
http://qsmile.com/qsimages/93.gif

[mescalin]

i would like to learn that also..for example İ to i or smth like that..