Almost no free space left on D drive, but files/folders only take up little space

Question

I'm using Windows 7.

All of a sudden from nowhere, my D: Drive is showing a red bar for space, and it says there are only 620 MB free out of 28.9 GB. Yet when I browse into D:, select all files and folders, right click, and choose "Properties", the total space taken by the contents of D is a mere 2 GB. I've already enabled viewing hidden files, but the hidden files are really small. What on earth is taking up the rest of the space? Or is the My Computer's browser falsely saying I'm almost out of space?

Edit

I tried the solution here: What's using up my disk space?

But I got this error:

Error: The shadow copy provider had an unexpected error while trying to process
the specified command.

Solution

I'm not sure why you would not be able to see the total space using your method, but when I'm running low on space on Windows, I've found WinDirStat to be very useful for figuring out why:

http://windirstat.info/

This is an open-source tool similar to KDirStat on Linux, if you've ever used that. It shows you a graphical view of your filesystem as well as the normal directory tree view, with total size and percentage of each directory and file. There are options to show "unknown" space used as well as the normal files and "free" space.

The help files for WinDirStat mention that "unknown" space could be "system restore" data from Windows, or "system volume information", or something else. So if you see a lot of "unknown" space I'd start looking at where your system restore gets stored. If it's not that...I'm out of ideas. You can see if checking the disk for errors helps.

Comments

[Doktoro Reichard]

It is possible some other user is using those files, and so, if he's an admin, Explorer wouldn't know about the files being used, if you were a regular user.

[user248968]

I am the admin user here, and the only other user on this laptop is logged out.

[Jan Doggen]

It helps if you specify what's (not) on the D: drive. Where's your OS?

[user248968]

Windows 7 is on C: