I'm not sure if you play AD&D, so my 1st comment may not suit your exact needs. I do reviews of RPG DM/Campaign software at my blog, and although the focus is for 1E campaigns, much of the software has been developed for multiple RPGs.

http://bloatedblowfish.blogspot.com/...tware%20Review

Next, if your looking for a simple software app to keep notes, I'd recommend NoteTab Light - a FREE robust Notepad style app, which can do HTML design if needed, but straight out of the box is suited for simple notes. On the downloads page you'll find the link near the bottom.

http://www.notetab.com/

Lastly, I carry a small Piccadilly notebook (with locking enclosure) that I keep notes in. Its very portable, and allows me to write down things on the go when inspiration hits. I then transfer those notes to NoteTab Light when I work on my 35 year old campaign.

Cheers,