Okay, here is it... it's little and primitive but can be usefully for someone :)

Is written in VB.NET 2.0 and using XML file as storage.
Without administration or managing, can be done only manually editing xml file.
Anti-bot as CAPTCHA code verification is included.

Working example can be found here: http://area-71.net/nanoXML/

and sources is here: nanoXML.zip (10.69 kb)