1. System Volume Information is a hidden folder in every partition of your hard disk. It is used by Windows System Restore tool to restore your computer. This folder stores the Restore points and all the deleted files which Windows will use at a later stage to restore your computer. It also stores the Chkdsk logs which is Disk Checking service of Windows. But sometimes when you create a restore point, the files infected with virus can also be stored in this folder and most Antivirus tools can't delete files from this location. So, if you don't use System Restore service, you should turn it off so that all the previously created restore points and stored files are deleted from this folder. 2. Recycle Bin as you know stores the files that are deleted so that you can restore accidentally deleted files later. Every partition on your hard drive contains a Recycler folder which not only stores the deleted files from that partition but also the location from where files were deleted so that they can be restored to correct location at a later stage. In windows XP and earlier, this folder is named Recycler and in Windows Vista and above , this folder is named $Recycle.bin. Your external hard drive may have both these folders if it is plugged first in XP, then in Win7 or vice-versa.