I can not remember the technical term for it, but the Windows 7 is running in its own separate 50 GB partition, as opposed to mixed in with the Mac programs.
Unfortunately I didn't have antiviral software installed - don't ask me why not. I've managed to install it now, with some difficulty. The virus was blocking my access to the relevant web sites. However I was able to get the installation program in through Dropbox. It's running now, and hopefully will give me an identification of the virus in an hour or 2.
As far as I can tell, the OS X side of the computer is running normally. However I guess it's best to get a Mac antiviral software to check that over.
From what you say, do you think my first option should be to delete the whole virtual machine and reinstall it?
NQueue