.net application working in 2003 server but having issue in 2012 server

Hi team,

I have application hosted in 2003 server and it works fine, now we want to port my application to 2012 server and i have set up my application. but when i try to download and run the exe being created, it throws error "Could not load file or assembly 'System.Drawing, Version=4.0.0.0, culture..", i have 4.5 and 3.5 frameworks on the new 2012 server. this error throws in our app start project. not sure what is the issue? Please guide 

Thanks,

Rajesh