LEGO has produced 4 different MindStorms sets. Each Kit can be used for a different number of the Challenges in this website.
NXT 1.0 Retail Kit – can use all Challenges whose numbers are less than 100.
NXT 1.0 Educational Kit - can use all Challenges whose numbers are less than 100, except that you need two Educational kits for Challenge 30.
NXT 2.0 Retail kit – many (but not all) of the Challenges will work with this kit; however there are known issues with the Robot building, and some Challenges. The compatibility of this kit with these Challenges in currently being checked.
RCX Kit – Unfortunately, these Challenges are not suitable for this Kit.
Not sure which Kit you have? Click on the menu headings on the left of this web page.