Since Windows 7 keys work for 32 or 64 bit versions, which version should I install in Parallels for the best performance? I don't plan on giving Windows more than 2GB or ram (if that), so that's not a concern. Is it 6 to one, half-a-dozen to the other? I'll be running this on a Late 2011 13" MBP with the i5 and 8 GB RAM. Thanks!