Vista and Windows 7 uses a very different video driver. It is infact very very much different from that of Windows XP. It improved performance but the down side is that it does not allow full screen console based applications to be launched.
Microsoft did launch a fix to downgrade the video driver to Windows XP but it is quite dangerous if things go wrong. So we might go for an alternative way. There are softwares which "emulate" the command prompt by software hence removing the need for windows command prompt completely. The user experience is not as good as the real one provides but it is still a decent solution to your problem.
Here is one: