Unable to start postgres service (8.4)

Hello,
I only modified the pg_hba.conf file. It is currently set on trust but 
the server still asks for a password (even tho when clicking properties 
the password field is disabled ) . I treied restarting and now the damn 
thing wont start at all (the server that is; i have no postgres 
processes now). I also installed  postgres 9.0 now and it works . But i 
would realy like to regain access to the old server. I have also tried a 
solution involving resetxlog -f but  to no avail

Regards,
Sam