Imre, if you have uninstalled XP Mode and deleted its files, it is no longer taking any space on your HD.
Differencing disks only means that by default, XP Mode uses two different vhd's: XP Mode Base.vhd
in C:\Program Files\Windows XP Mode\
, and Windows XP Mode.vhd
in C:\Users\Your_Username\AppData\Local\Microsoft\Windows Virtual PC\Virtual Machines\
Differencing disks can be fixed size or dynamic. For instance in XP Mode's case, one of the two vhd's used (the base vhd) is fixed size and the other is dynamic. Using differencing disks have nothing to do with how much space the vhd takes from host HD. A fixed size vhd takes its actual size, a dynamic vhd only what it needs.
A dynamic vhd only allocates as much HD space as it needs. If your Hungarian website tells XP Mode allocates 127 GB of HD space, it's simply not true.
To make this even more confusing
Let's say you have 50 GB free on your HD. You can create a Virtual PC virtual machine, creating a dynamic vhd of 127 GB, more than the free space you have. You install Windows 7 to this virtual machine, which takes about 15 or 16 GB. If you now check your host, you'll notice that you still have about 35 GB of free space because the dynamic vhd only takes the space what it needs, in this case 15 GB. But when you run the Windows 7 virtual machine and check the HD size, it shows it has a 127 GB HD.
So, you have created a dynamic 127 GB vhd on a HD which only had 50 GB free space. Your new Windows 7 virtual machine is allowed to expand its vhd up to 127 GB, but in this case it can expand only to about 50 GB because then there's no more space on your HD for the dynamic vhd to expand. If you want to really use the full 127 GB, you have to delete something else from the HD so that the vhd can expand to its maximum size.