I want to register and download my antivirus with spy sweeper from Best Buy and download.

The keycode should be on the box it came with.

Use Comodo Anti-Virus, its free and it is better than spysweeper

try another internet browser. if that won't work post a comment and i will see what else could be the problem

On Feb. 12, 2008, Microsoft released an update that fixed the recent compatiblity issues between Windows Vista and Webroot Antivirus/Spy Sweeper that were a result of a previous Windows Jan. 8, 2008 update.
Recommended Fix:
To fix this issue, update your copy of Windows Vista with the latest updates available as of 2/12/2008. For many users, Windows Vista will update automatically at its next scheduled time, but the update is also available as a manual download. See below for instructions on how to update Windows Vista.
We also recommend updating your copy of Webroot Antivirus/Spy Sweeper. The latest version does not experience any compatibility issues and it is generally recommended that you update your software to the latest version in order to ensure maximum security and protection of your PC.
Click here for help on how to update Webroot Antivirus/Spy Sweeper.

if you know registry editor then go regedit find all webroot stuff and delete

With some applications the publisher only wants the user to register using the free copy. tried contacting the publisher via their website or your application should have a registration link which will take you straight to the website

remove Webroot Spy Sweeper
http://resnet.bridgew.edu/files/SSECleanup.zip

and then download an another anti virus from
http://www.filehippo.com/software/antivirus/

first uninstall the webroot spy sweeper through the following steps.
1.click start 
2.go to control pannel
3.open 'add or remove program'
4.a window will open wait for some time until the list is populated

5 i)in that list find webroot spy sweeper and click remove 
   go through the uninstall wizard and finish the uninstallation process

5 ii)if you didn't find webroot spy sweeper there then it can be a virus
You need to download a program called MalwareBytes because that searces your entire computer
, finds the virus and completely destroys it.

http://www.download.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html

Click the green 'download now' button (don't worry - this is free) and once you've downloaded it, got the updates and done a system sweep which takes a long time but it's worth it, you should be fine. It also solves the desktop, wallpaper and screensaver hijack, too.

6. restart your computer

7.open mycomputer click search and do a search for webroot spy sweeper
delete all the files and folders regarding webroot spy sweeper

8.now download mcafee before installing mcafee uninstall MalwareBytes and restart your pc
because at a time only one antivirus software should be used

i think this solution will help you 
if the problem is not fixed please inform i will suggest some other ways

Spy Sweeper is for spyware and that is not the same as anti virus software..If you do not have anti virus software, you should consider a getting one of the more popular types such as McAfee or Trend PC Cillin.these are two readily available types .. It is good to have both spyware and virus protection and they are not the same.. Hope this helps you..

what errors are you getting?

if you wish you can try AVG antivirus and Avg anti spyware,, its one of the best out right now and highly recommended and best yet they are both free