These ISO's get cached on various ISP servers for bandwidth reasons. If the copy the you're getting from ISP has a corrupt copy then you may get the same corrupt ISO over and over. You can try going to a coffee shop or across town or some other location
and you may get a different or good download.
You can contact dreamspark directly here.
https://www.dreamspark.com/Student/Support.aspx
Regards, Dave Patrick ....
Microsoft Certified Professional
Microsoft MVP [Windows Server]
Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.