Since you require so much information to sign up, you could really use a demo or a video of the site in action. Also, the free version is too hidden, I almost left the site, thinking that there was no way to try it for free.
Acoustic guitar, recorder, ukulele, djembe. I have a small collection of folk instruments and try to learn to play each one of them at least a little bit, so I can play (or at least produce semi-musical sounds from) things like duduk and rababah :)
Requires software install? XP only? WinAmp only? 15-days trial? Guitar only? I don't think so. 90-s called, they want their software development business model back.
Find a Tai Chi studio and learn the short form. It is a complete set of exercises for back, legs and shoulders that takes about 5-10 minutes to complete. And it is fun to do.