My preference is to not use the Download Manager - but rather - download the install files that are the same as having an install DVD or USB.
Make sure you also run the registry edit for the Microsoft KB problem.
Make sure you have MS Excel installed and run at least once.
Make sure you have UAC and anti-virus temporarily disabled.
One, you need to delete your attachment. It contains information that shouldn't be public.
Two, you need to find out from your school which version of SolidWorks you are entitled to. Obviously, going off of the error messages, 2015 isn't it.