With each new install of the client, you are given a new node ID. Each time you re-install the client, you will have another node ID.
This can result in several "inactive" ID's on your stats.
To avoid this, copy file
to a different folder. (Adjust for appropriate path.)
When you reinstall - just copy that file to the same directory it was before and you will not have to add another node to your stats.
If you do reinstall, and find yourself with a new node, simply go to this page and register it.
There is a helpful thread in the TSC forums here.