First of all, I would like to say "thank you" to anyone who can help me in any way. Here is my problem: I have a desktop running on XP that I want to upgrade to Windows 7 Ultimate. I had the system assembled around '08 by a friend of a friend, whom I have no way to get in touch with any longer. I was quite happy with the XP and had no wish to pay for a windows 7 upgrade. I'm fortunate that I found this forum recently and it prompted me to do a windows 7 clean install. Being a person with zero experience when it comes to computer, I did not make any backup before attempting the clean install. I read that I can revert back to XP as long as I have the windows.old files available and thought that would be enough. Everything went smoothly with the installation process and I now have a running Windows 7 Ultimate 32bit system. I opened the computer and found out that my C drive is out of space! There is only 84MB free of 40GB! I opened the drive and found a bunch of folders along with the windows.old folder. I know the windows.old file would take up a lot of space, but I'm not sure why there are so many other folders (See attached picture). I've also done a clean install of windows 7 64bit on a laptop, but this time I've formatted the C drive before installation, so on my laptop C drive doesn't have a lot of the folders that are present in the desktop. Which makes me wonder...are all those folders from the XP system, and if so, why aren't they inside the windows.old folder? I originally thought if everything works fine with the Windows 7, I can just delete the windows.old folder and continue with the new system, but now that I have a bunch of extra folders lying around the C drive, I'm not sure what would be the best way to delete all the old stuff. Would you recommend me to just perform a clean install again, this time formatting the C drive? My other problem is with device manager. After I finished the installation, I went to nvidia's website and downloaded the driver there. After a successful installation, I opened up device manager and noticed there is a "PCI Simple Communications Controller" under "other devices". Can anyone tell me what that is in general? I have no idea what other drivers I need to update since someone else assembled the whole system for me and everything appears to be working fine. The only things I know for sure are the Intel Core 2 Duo E6750 processor and the Nvidia Geforce 8600GT card. My last question: I have an external HDD that I use to store my pictures and music. Now that I've started paying more attention to computer maintenance, I would like to do regular system backup. However, what exactly am I backing up and how do I go about doing it? Like I said I keep all my data on the external HDD, so I just want to create backup for the operating system in case something went wrong. Is this more ghosting than backup or are they the same thing? Can someone explain to me in dummy language please? And... can I use the same external HDD for backup and at the same time continue to store photos and music on it? Sorry if this is a lot of questions. I'm just beginning to learn about computer and maintenance. Thank you for any help! Happy new year!