When you attempt to install an OS from a previous one, you have the option to partition your HDD. If you choose to do so, everything is wiped. If not, then Windows creates a folder that contains some of the previous settings and files you had from your last OS. This folder IS NOT needed in order for you to run your new OS, and can easily be deleted.
To do so...
1. Click on your Start button on the task bar.
2. Type in/go to Disk Cleanup.
3. Once opened it'll ask you to select a drive. Select the one your OS is installed on.
4. From there, you'll see a list of files that have accumulated on your system from the result of normal usage.
5. Just below that, you'll see a button that says "Clean up system files". Click it.
6. Another box should prompt you for a drive to select, just select the same as before.
7. After scanning, another window should pop up and on the list of files select "Older versions of Windows", along with anything else you want to clean up (temp files, error reports, etc)
8. Click Okay.
And that's it! That should take care of the folder, as well as clear up a few GB's on your HDD.
Let us know how it goes!