DR download manager won't run

I've bought the Student 32-bit version of Win7. I received a confirmation email with my order number and Key.
Successfully downloaded both the .exe file and the ISO file. I don't want to run the ISO file if I can possibly avoid it BUT the .exe file doesn't run. The Digital River download manager opens, and then says that I need to be connected to the Internet for it to run...when i AM connected! So I don't even get as far as putting the key code in.
Found the Customer service button, which asked for Oder no or email address + last 5 digits of credit card details - it regognises neither of these. I'm pretty sure I bought it directly from the Microsoft website, so perhaps the exe. file is corrupted? Still doesn't explain why it doesn't recognise my order
Any ideas?
I've also tried rebooting but makes no difference

beaskies