Once you've downloaded the MATLAB R2011b installer:
If you or your institution ever purchased a license for R2011b—either as a standalone license or under a subscription that was active in 2011—you can still download it directly from MathWorks. matlab r2011b download
before running the installer so it can automatically detect the product files. Installation & System Requirements Where can we download R2011b? - MATLAB Answers Once you've downloaded the MATLAB R2011b installer: If