having problem in installing matlab ?

hello , i m trying to install matlab that i have bought from mathworks.com and instead of solving my problem , its pushing me into one . when i tried installing it ,it shows , a message .....

it is : One or more of the following products are required to proceed with the installation: MATLAB 8.1 (Not available). You must select a folder where at least one of these products is installed or select these additional products for installation.

[Walter Roberson]

Contact Mathworks for free installation support.