Windows Vista Ultimate x64 SP2 fully up-to-date size?

I'm restoring a computer for a friend, as he managed to corrupt his Windows installation while messing around with a partition manager. He asked me to partition his drive for him (which I plan to do properly), but neither of us are sure on how to partition the drive sizewise. Including updates. Considering that Vista updating is basically dead with 7 out now, what is the SMALLEST possible system partition that I can allot to Windows Vista? 
 
Basically, my task for the community is to find out what Vista takes up on your computer right now, fully updated.  I presume an extra 5GB will suffice for SP3 and future updates.

I think its 10gb for a new vista install give or take.  The big problem is not updates really but the winsxs folder in the windows folder.  Its basicly the windows compatibility folder and fix for dll hell.  I have seen a few with that folder being 10-15gb. Iits sitting around 7gb on my machine at the moment.  So to answer your question i think 20 should be the smallest you could go with but recommend 25-30.