What's a good way to run a virtual copy of Ubuntu on Windows 7?

You can download VirtualBox to run a virtual copy of Ubuntu.

Download a disk image of the Ubuntu 64-bit install CD here. Then open VirtualBox and create a new machine with the disk image as the start up disk.

I use this to run Ubuntu on Windows 7 every day and it works very well.

You can use VirtualBox and if you really just want Ubuntu for the software i.e. rather than for the whole Unity interface based experience, you might consider Lubuntu instead.

http://lubuntu.net/

Lubuntu is simply the official LXDE version of Ubuntu and while its spartan blue/grey looks may not win any beauty contests, it does work a lot better than other forms of Ubuntu in VirtualBox.

LXDE is a desktop environment designed for less capable hardware and therefore it is quite suited to virtualisation software, which typically isn't able to use your hardware as efficiently as a bare metal installation.