Upgrading from Windows Vista to Windows 7 should be relatively easy. 

During your installation process of Windows 7 you will see the upgrade option which you should choose.  The good thing about upgrading is that you are able to keep your files, settings and programs for Windows Vista.  I would still make a back up of everything just incase in an external harddrive.  Some users might not be able to upgrade to Windows 7 due to their previous Windows installation. For instance, if you have a 32-bit version of Windows and want to upgrade to a 64-bit version you wont be able to. 

 If you need to find out which Windows 7 installation disc you should do then, do the following:

1. Open Performance Information and Tools by clicking the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking Performance Information and Tools.

2. Click View and print details.

3. Under System, you can see what type of operating system you’re currently running next to System type, and, next to 64-bit capable, whether you can run a 64-bit version of Windows.

4. If your computer is already running a 64-bit version of Windows, you won’t see the 64-bit capable listing.