>>>I will give C: 500 GB and split the rest between D: and E:. Right now the C: is about 260 GB so I will have plenty storage for the future software.
>>>Thank you very much for your suggestions. While tomorrow some people will be watching this "unimportant event" :), I will be doing something very important :)
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>>I always try to minimize the OS/C: partition size. I have an xCopy directory outside C:, where all portable software gets installed, which can be used by VMs as well. In dedicated VM C: is between 40 and 90 GB, in long-running machines still below 120 GB.
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>>As I try to never use documents and settings, only programs need more space, and they are frugal compared to media stuff ;-)
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>Sorry that I don't understand something simply to you. If I want to, at a later date, to install a VM software, will I be able to install it on the existing C: (OS) partition? (provided, of course, that this partition has free space)

Yes. BUT personal experience is that the probablity of screwing up the partition into something unusable is 5 to 10 times higher with the C: partition than with DATA ones. Therefore I reccommend putting the VM files EVERYWHERE BUT into physical C:.

Before VMs I set up each machine as multiboot: if one OS partition was scrambled, I could finish pressing jobs with the other boot option.

You can give each VM (restrictive) access to parts of physical macines directory, similar to creating a SMB share. That way xCopy and Install folders from physical are setup as R/O for my VMs.