Open up regedit.exe through the start menu search box or by pressing WIN + R to open the Run box and typing it there, and then locate the following registry key:
Now you can find the RegisteredOwner and RegisteredOrganization keys in the right-hand pane. Change them to whatever values you want.
To show off the new changes, just type winver.exe into the start menu search box or WIN + R run box to see the About Windows box:
Kinda useless, but one of those things I have to write about if I want to cover everything :)
This should work in all versions of Windows, including Windows 7 and Windows 8.