Windows 7: XP Mode disk full error

Hi,

I'm running XP mode on a 31 Gb (E:/) partition of a 500 Gb Harddrive on a Windows 7 Ultimate x64 computer. In XP Mode the (local) C: drive reports the availabillity of 126 Gb? Although there are only a few programs installed on virtual XP, the computer keeps telling me that the E:/ drive is full. It looks as if this announcement is produced by Windows 7 and not Virtual XP. I further found that the file Windows XP Mode.vhd (which should be the actual virtual machine) occupies some 29,9 Gb. This could be the reason the E:/ drive reports to be full. However as there are only some 10 Gb of programs stored on the virtual machine (incl. XP), there seems to be no reason why the *.vhd file should occupy 30 Gb. Does anybody know why this file is so big and how I can check what makes it so big and how I can reduce the size?

Kind Greetings,
Dave
Netherlands