Today, after finally taking the plunge into the Linux world (I'm trying to refocus my work to the Rails ecosystem), I installed VirtualBox on Linux Mint 13.
Simple enough, a little visit the software center and done.
I created my new virtual machine and tried installing Windows 7 from my .ISO file but behold a glitch!
Windows failed to start.
A recent hardware or software change might be the cause.
The fix is real simple.
All you have to do is open the settings for your virtual machine:
System > Enable IO APIC
Save your new changes and launch the virtual machine again, everything will now run smoothly and you'll be able to install Windows 7.