If you have Qwest DSL service, you need to cancel your current paid OneCare subscription and then use your Qwest LiveID, according to their support site,
http://kai03.qwest.com/WindowsLive/MemberCenter/DownloadOneCare.aspx, typically @q.com, to activate your free subscription. You can cancel your paid subscription by contacting OneCare support. If you were recently charged for renewal, you can probably get a refund for that renewal charge.
Note that I would recommend uninstalling OneCare and then reinstalling and activating the free Qwest subscription first, to be sure that you don't encounter any problems. Then, cancel the paid sub.
One problem that you may encounter - if your paid subscription LiveID is your Qwest LiveID, you may have a problem activating the new free subscription, since you will already have one that is paid.
Here's the order of events (after confirming that you are entitled to a free subscription via the Qwest partner deal - I'd call them if there is any question):
1. Open your current copy of OneCare and follow the path described here -
http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90to get to the support options page where you can make a note of the current subscription LiveID and also the customer service phone number - you won't have access to that number after you uninstall!
2. Uninstall OneCare from the PC via Control Panel/Add or Remove programs
3. Reinstall OneCare from
http://onecare.live.com and activate with your Qwest LiveID. Contact Qwest if you encounter problems.
4. Contact OneCare support, using the phone number obtained in step 1 to cancel the current paid subscription.
Good luck.
-steve
Microsoft MVP Windows Live / Windows Live OneCare Forum Moderator