How Can I See Data Stored In Sys Drive (But In De Directory)

I see in Disk management add-on that there is around ~20GB of data on my physical system drive. 

I ll attach a screenshot so that you can see.

I want to move over to WHS 2011 but I want to make sure I get that 20GB of data before making the installation, where should I look? I did not find anyting in C:\fs