Size on drive mystery

When I add up all the size of all subdirectories such as Program Files, etc.
(by right click/properties), I get 100 GB. But when I do the same for the C
drive (the only drive), I get 130 GB of used space. Where is the difference?

Thank you for your help.

Vista Home Premium 64 SP1

Erik wrote:
> When I add up all the size of all subdirectories such as Program Files,
> etc. (by right click/properties), I get 100 GB. But when I do the same
> for the C drive (the only drive), I get 130 GB of used space. Where is
> the difference?
>
> Thank you for your help.
>
> Vista Home Premium 64 SP1
>

System restore?

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