How do I determine the type of protection against the virus responsible is based on my computer?

In here you can select to check what antivirus programs you have

Norton live Safe Mode virus scan
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1. Go to this link, below, and save it in your favourites. Save it up at the top of your favourites drop down list, otherwise you may not be able to see it in safe mode. (drag it to the top).
Close the window
2. Turn off popup blocker on your browser or software.
3. Turn off system restore as long as you are confident you don’t need it.
Right click my computer icon >properties >system restore tab > turn off.

This will delete all restore points. (System restore can harbour virus)

4. Boot in safe mode with networking by tapping f8 key in the first few seconds of turning the computer on.

5. Using your browser in safe mode with networking. open your browser and go to the link, choose antivirus scan, it will take quite a time to install but stick with it. It will ask to install active x controls which also take a while to install. Don’t interfere, just wait a while. Run the scan when it asks. You can also run the antivirus checker afterwards all while in safe mode.

6. Reboot normally, turn on system restore and create a restore point.

http://security.symantec.com/sscv6/default.asp?langid=ie&venid=sym