There is a possibility that even if you have installed the guest additions in virtualbox, the resolution of the guest OS won’t exceed a certain value. If that’s the case you can use the VBoxManage command to set the max resolution like this :

If you have forgotten your mysql root password all you need is the root password of the system to create a new one.

This one troubled me for a long time and it also resulted in a corrupted database at some point, because i changed collation encoding to utf8 but the database encoding was latin. (so always make backups and make sure you don’t erase them :P )