Logbook Pro. Support this site and get an excellent logbook program.
Do a search on PC logbooks and you'll find a bunch of threads about them.
I wrote my own in Lotus123. I upgraded it to QuattroPro. I converted it into Excel, then Access. What a waste of time. I upgraded to LogbookPro, imported my database, and was set. I get tons of features, especially the PDA data entry, for less than half an hour of flight time.
I have used the demo version of LB pro, and although the interface looks pretty, I was slightly dissappointed with the fact that you have to 'click' then type in the times. It would be better if you could set the interface up to allow you to simply type in the times etc without having to click-enter them.
Also, I have tried using Excel, but I cannot seem to get it to calculate flight times when I give it out and in UTC times. You think it would be a simple process, but noooo...