UserID
From FaHWiki
The UserID is a 16-digit hexadecimal value which Stanford assigns to your client so that the servers can recognize your unique machine. It is unrelated to the UserName (which you assign yourself and) which is used to collect the points into an account. The CPUID (UserID + MachineID) identifying your client can be modified by setting the MachineID. This is unnecessary if you have a single CPU in your machine. If your machine has more than one CPU, you'll probably want to run a separate client for each one, and the value of the CPUID must be unique for each client.
Note: If you need to ghost/copy the HDD then all you have to do to still use the FAH client, is to remove the UserID value from the image. Either before imaging of the HDD or after. Folding-community: alancabler in Two Windows machines with exact same ID.
See also: the CPU ID field in the queue.dat file
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