I don't have or want Vista so I can't try this out. My computer does not have enough RAM to run Vista in a virtual machine and I don't want to run any Vista-XP dual boot. If someone has Vista and can verify that this works, that would be good.
This is from this site:
If you want to be able to use QBASIC in full-screen mode, and you got an error message when you try pressing Alt+Enter, then you must use Vista's "Standard VGA Graphics Adapter" video driver (as described in the next paragraph) instead of whatever driver you or Windows installed for use with your video hardware. (Alternatively, if your hardware makes this possible you may want to install the Windows XP driver for your video hardware as described below).
How to install the Standard VGA Graphics Adapter in Vista: Right-click on the Windows desktop; choose Personalize from the pop-up menu; choose Display Settings from the Personalize dialog; on the Monitor tab, click Advanced Settings...; on the Adapter tab, click Properties; on the Driver tab, click Update Driver...; click on "Browse My Computer for Driver Software"; click on "Let me pick from a list of device drivers on my computer"; in the "Select a device driver" list, scroll down to Standard VGA Graphics Adapter and highlight (select) it; click Next. If your monitor goes blank, wait five minutes, then power down your computer and restart it normally. If your monitor does not go blank, wait while the driver is installed; click Close; then continue to press Close or OK or otherwise close dialog boxes until you are back to the desktop. If you are prompted to restart your computer, do so. You probably should do so anyway. (If you want to reverse this procedure, follow the same instructions, but let Windows automatically install the appropriate software for your system instead of browsing your computer for driver software.)