Smallest windows installation?

I have a MacBook Air 128Gb, so disk space is obviously very important to me...

What is the smallest possible windows installation I can get? I only need to be able to run one windows application, and I don't need all the rest of the junk that comes with windows.

Currently running OSX Lion with PD9 and Windows 8.1 preview. This is taking up 23Gb.

Any tips on how to reduce this?

 

If I have to, I don't mind running windows off an external drive. This will save me a helluva lot of space, because all the files that I need the windows application for can be stored there too.

Will a USB3 External HDD be fast enough?

 

Any answers here???

 

You can change the path to a new Windows Virtual Machine on the "Name and Location" panel while creating the new VM. Using an external drive or a thumb drive will both work. You can also move the .pvm file of an existing VM from the default /Users/(your id)/Documents/Parallels to a USB drive. Double click on the .pvm on the drive and it will register in Parallels.

Rick.