Sql Server enterprise manager

I have upgraded our sql server from version 6.5 to 7 using the upgrade wizard supplied on sql 7 cd. however now when i try to create a database, table,diagram ect in enterprise manager i keep getting the error "unexpected error has occured" and it will not let me go any further. i can create tables using transact-sql okay but with enterprise manager not working i am worried the installation may be unstable.
i know the error message does not tell you much but that is all i am getting.
Do i need to uninstal sql altogether and if so what do i need to do to fully uninstall ?

thanks in advance