I just bought webroot from BEST Buy and cannot locate the Download Now button to enter the key code.

I would definitely suggest a better protection but usually when you go into file explorer and go to downloads double click on setupwiz for webroot itll prompt you for the key.

Both Best Buy and Webroot Support can provide you with assistance. The most common cause of Best Buy Keycodes failing is when Best Buy does not activate them at the time of purchase, so checking back with Best Buy should be your first bet. If that does not resolve the issue, Webroot support can be reached in the US at 1-866-612-4268 and various other numbers internationally.

If you have the official key which you paid for you can download a trial version of the software from Webroot themselves http://www.webroot.com

Go to the website in the search book at the top right hand side type "download" and click ok.

Once you have downloaded and installed you can the convert the trail into the full version with the key which came with your purchase.

Contact WebRoot they will walk you through the process on line.

You can request for your key again and they will send it back to you through your email.
You can file you request through this link : http://www.webroot.com/updates/redownload/index.php

Take a moment to download and install CCleaner & Advanced system Care from download.com You only need the free versions of this software. If after running these programs you still have issues try resetting IE/Firefox's Defaults by going to the tools and settings options and click reset/default were applicable.