No, the only way to add a PC is to install it on that PC.
If your PC is already infected, then installing any antivirus product is going to be futile.
Have a look at this post in the MSE forums:
http://social.answers.microsoft.com/Forums/en-US/msescan/thread/87058857-d181-4019-a723-efd9a49d9275
If you are in North America, you can call 866-727-2338 for help with virus and spyware infections. See http://www.microsoft.com/protect/support/default.mspx for details. For international information, see your local subsidiary Support site.
-steve
~ Microsoft MVP Windows Live ~ Windows Live OneCare| Live Mesh|MS Security Essentials Forums Moderator ~