virtualbox.org

Installed Win7 guest on Ubuntu host without problems. No guest addition installed yet I've screen resolution from 800x600 to 1600x1200 to choose.
After installing guest additions I've only one screen resolution - 800 x 600.
Resolved by uninstalling guest addition and I'm back in range 800x600 ~ 1600x1200.
But IMHO the most embarrassing thing for virtualbox developers: I found web discussions/gripes about the same problem 8 yrs old. What a great progress!

It might be embarrassing if you provided some actual evidence and diagnostic information. Without that... you're welcome to say whatever you like as long as you stay within the forum guidelines, but don't expect anyone to help you.