Hi, i need to vaccuum, etc, but cant get into pgadmin III

Everytime i try a password, eg postgrespass or dbpass or anything else i may have tried, it gives me the 'an error has occured, cant open file pgpass.conf error 5 access is denied)

Strange thing is i have edited the .conf file from md5 to trust, and i assumed that all of postgres then didnt have any passwords required.

Any ideas?