The 8059 error should show you a message that explains that you need to activate with a LiveID if you already created a subscription for that LiveID. The product key can only be used the first time to create the subscription. Subsequent installs use the same LiveID as the initial install. If you use a different LiveID (email address) you will be prompted for a key or payment information.
The LiveID for your subscription can be found under Help/About - Subscription ID on an activated copy of OneCare.
If you don't recall the LiveID you used for your subscription, you will need to contact support who can provide that information to you using your Key and/or contact information.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
Alternatively, sign in at http://billing.microsoft.com with email addresses that you have set up as LiveIDs and one will show your subscription listed - that would the LiveID to use to activate.
If this is your first installation, and you have never activated, and you encounter the 8059 error, please contact support or see if you can exchange the retail copy of OneCare for a new copy as it would mean that you may have a duplicate key.
-steve
