Both SKU's have Windows XP Mode available (XP Mode can be used in Professional, Enterprise and Ultimate). Paul Thurrott has written a great comparison of the features in each Windows 7 SKU. THat article can be found here:http://www.winsupersite.com/win7/win7_skus_compare.asp
Thanks, I think that pretty much made up my mind. I'll go with Pro for now as it looks like that has all the features I need. I didn't know the Pro had the XP mode, thought it was only the Ultimate version.