Why is the total size of my files on Windows 7 more than total disk size?

I have a virtual machine with Windows 7 x64 quest OS. When I boot from PE OS CD and run file manager (Total Commander) I see that the total size of my files on virtual machine is more than total disk size. What is the reason?

EDIT: My Windows folder size is about 11.4 Gb while disk size is 10.3 Gb. And WinSxS folder size is about 6 Gb.

Solution 1:

Total Commander must not be aware of linked files; Windows has functionality similar to symlinks in *nix environments. So the same file can appear in multiple locations.

Either that or you've got NTFS compression turned on somewhere and that's reducing the size on disk vs the file size.

Solution 2:

It is because hard links to WinSxS components have the same size as real components and included many times...