You didn't know what to do at the time.
Having said that, have you checked that the downloaded installer isn't still on your hard drive?
Go to the directory where your downloads exist and check if the installer is still there, it might be called 'Setup'. If you have more than one file called 'Setup' you can easily activate each one in turn then cancel it when it appears at the EULA screen. That way you can figure out what each one is for. You can even change the file name to that of the program if you want to keep the installer files for just this purpose.
If you have deleted the installer file, because you paid for the online download, you can go back to Microsoft and download it again for free. They SHOULD keep track of who they sell their product to, and having already paid for it you have unlimited access for the life of the program.
I personally have not paid Microsoft for an online download of any of their products but do have experience of other 3rd party software companies' online downloads. They allow purchasers to download again for free if the need arises. :)