I haven't seen Win 7 using up HDD space as fast as Vista was, and M$ did say they had optimised it greatly, so maybe (hopefully) they actually fixed this issue and you will be OK. I currently have a 400GB partition for Win7 and its still got 319GB free, and that is with a lot of software installed, including the full Office 2010 and Adobe CS5 Master Collection, which consumes a far amount of space. But even so, that is still taking a total of 80GB up already in total. Might be worth you using a partitioning tool and increasing the size a bit just to be safe.