Personally speaking I have usually used
Partition Magic with the best of luck. As far as the size, I would say to increase it to utilize the entire drive space. If you want to have another location to safely store or hide things, best bet is to have a secondary hard drive for that use. I have always kept a large hard drive hidden from the web to use to back up everything else to that location. then I have kept my main hard drive smaller(160 gig currently) and another one of about the same size(250 gig) all backed up to a 1Tb backup drive.