Yes, you should be able to reinstall Equipt completely, but it would need to be removed first. If it is partially removed, you may be able to get the OneCare parts completely removed by using the cleanup tool -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=828910&SiteID=2
Once you've removed OneCare, try the install of Equipt again.
If the rest of Equipt is fully functional, but just OneCare is broken, use the cleanup tool, then reinstall OneCare from http://onecare.live.com and activate the subscription with your Equipt subscription LiveID.
If you need more help with Equipt -
http://www.microsoft.com/equipt/support/default.aspx
-steve