Ever had a server that seems to run out of space only to find the the System Volume Information folder is using a TON of space?

Volume Shadow Copies were the problem in our case. Here is a link to explain exactly what Volume Shadow Copies are:

http://en.wikipedia.org/wiki/Shadow_Copy

For some reason there are some processes (backup agents, SQL services, etc) that create Volume Shadow Copies on Windows servers but then never delete/release them. When this happens your hard drive will start to fill up. Usually you can delete these Shadow Copies from Windows Explorer, but sometimes they don't show up there. In that case you can try using the vssadmin command from a Windows cmd.exe shell.

Sometimes vssadmin doesn't work either. If that's the case, the instructions in this forum thread worked for us:

http://www.vistaforums.com/solved-do-delete-shadow-copies-t3532.html

The breakdown is as follows:

1) Open an elevated command prompt ("cmd" + ctl-shift-enter)

2) At the command prompt, type "wmic", after some time "wmic:root\cli>" will appear

3) Type "shadowcopy", 4) it will display a list of existing shadow copies

4) Type "shadowcopy delete"

5) one by one, it will give a "Y/N" style prompt, confirming the deletion of each individual shadow copy.

6) Type "exit" to get back to normal command prompt

The Volume Shadow Copy service must be at least in Manual Startup Type or the wmic command will not work.

Have fun.