If you try to install a program such as Windows Defender or Adobe Reader and you get stuck with an error that indicates this: Invalid Drive G: and four numbers which would be formatted like this: xxxx, you’ll want to go into your registry and go to the User Shell key. There you will probably see some folder being assigned to the drive G:. In this case, you need to change that or re-attach whatever device that is in order for you to be able to install those programs. If you don’t have anything attached and never had anything attached in the first place, just go ahead and change the value of the item that has the G: drive letter to whatever it may be such as: C:\Documents and Settings\User\My Pictures. Do not use “%USERPROFILE%\My Pictures” as this won’t work – well it didn’t work for me. Who knows if it will work for you. In any case, I just went ahead and did the C:\Documents and Settings\User\My Pictures and once I fixed all the entries that had the drive G: I was able to install the two mentioned programs, Windows Defender and Adobe Reader 8.