hi,
you can edit registry settings for font type or color.
HKU\
S-1-5-21-1292428093-1957994488-1343024091-1004\Software\Microsoft\MSNMessenger\PerPassportSettings\<your passport id>\IM Color
(maybe bold text is different for you)
you can screenshot you registry,then change your font
screenshot again and compare
but i don't know how can you change.shell script or something.
RegShot:
http://www.majorgeeks.com/download965.html
(sorry for my english)