Hi brown,
Thank you for posting in Microsoft community
****From your issue description, I understand that you are having two windows folders in local disc. Please let me know if you are not facing this issue.
Did you format and install windows or parallel installation on the same drive?
Usually when you don’t format the drive and perform installation you will get windows O folder. If you have backed up all your data, I would suggest you run disc cleanup.
Description of the Disk Cleanup Tool in Windows XP
http://support.microsoft.com/kb/310312
Note: When you run disc cleanup on hard disk by searching your disk for files that you can safely delete. You can choose to delete some or all of the files.
Hope this information is helpful and do let us know if you need further assistance with Windows in future. We will be glad to assist.