On my installation of Ubuntu 14.04 in VirtualBox, the only screen resolution available is 640 x 480. I have tried the solutions suggested in this answer, but none of them helped. All of the answers there are about installing the Guest additions, virtualbox-guest-dkms, but that doesn't make any difference on my system (Win7).
Could you please post your answer in the original question? (as titles are the same) so we can merge them– Sylvain PineauFeb 28, 2015 at 17:33
I wanted to, but I wasn't allowed - too few "trust points"... :-(– Per Quested AronssonFeb 28, 2015 at 21:19
I have moved it now. Thanks for "enabling" me. :-)– Per Quested AronssonFeb 28, 2015 at 21:26
After having first installed the Guest additions, which didn't work, I found a solution elsewhere: linuxbsdos.com.
Use Xdiagnose from the Dashboard. Search for and launch Xdiagnose, then enable all the options under the Debug section. Click the Apply button, then close the window and restart the system.
That's what finally did the trick! Now I get 1024 x 768 instead.