If you have an active subscription to OneCare, you can install it as many times as you wish, as long as it is not installed and running on more than 3 computers using the same subscription LiveID.
I don't know what "2000" is, but if you are running XP SP2 or later, or Vista, you can install the trial of OneCare from
http://onecare.live.com and then activate the installed copy with your subscription LiveID. You can verify the status of your subscription by signing in at
https://billing.microsoft.com Be sure to fully remove Norton before installing OneCare. You may need to use the Norton removal tool -
ftp://ftp.symantec.com/public/english_us_canada/removal_tools/Norton_Removal_Tool.exe
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://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
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 with.
If the activation dialog already contains a LiveID from a prior attempt or one used in trial mode, but this is not the one you need to activate with to associate it with your subscription, see this post for how to reset this - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/f5ce50e4-9165-40a5-891b-fe5d0659738b
For more information see Instant Help - http://help.live.com/help.aspx?project=onecarev2&mkt=en-us&querytype=topic&query=OneCare_PROC_FindLiveIDHelp.htm
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator
