Changing database encoding, how to?

[JaFaRZuaBi]

helo everyone scripters/coders

I used to use Windows encoding in my website, now everyone is changing to UTF-8
when I open the forums it just gives me some symbols and I need to change the encoding to UTF-8
ajax doesnt work with windows encoding also
I need to change the whole data base to use UTF-8

is there any script for that ?
is there a way ?
the database is around 180MBs

thanks in advance