Okay, I will make some suggestions, not sure if they will make it work.
First, make sure that Impulse in not on your computer. Go to Add and Remove function in Windows and make sure nothing in there for Impulse. If you have a cleanup program like CCleaner run it and clean up the registry also. If you don't have CCleaner it is free.
Second, reboot your computer.
Third, turn off you A/V software. I don't know if .net is backward compatible and forget what version Impulse needs. I can't seem to find it to see what I have installed.
Fourth, go to the Stardock.com Home Page and try downloading Impulse again and reinstalling it.
As I said this may work or may not. Some A/V software has shown to screw up trying to download Stardock stuff. Running a cleanup prgram, as I'm sure you know, gets rid of hopefully anything related to Impulse.
I also run Win 7 64 bit. I have not had any problems in downloading anything from Stardock.