Depending on what you want to acheive, there are a number of options available to you:
1) If your ubuntu box is going to be a server of some kind and you only need to access the shell, you can use putty on windows to ssh into it.
2) If you need a bit more, take a look at setting up vnc, which will give you a graphical login to your ubuntu box from within windows.
3) If you don't need a separate box for ubuntu and your windows rig has some ram to spare you could try VirtualBox or VMWare which will allow you to create and run a virtual machine with ubuntu from within windows.
4) As above, but instead of using a virtual machine, ubuntu now comes with something called "wubi" which allows you to install ubuntu from within windows so that you can dual boot without the need to repartition your harddrive.
Last edited by sgmeunier; 12-21-2008 at 09:15 PM.
Reason: Edited behaviour of wubi