I've had the need to use these two tools for lab and testing purposes and have found a couple of points about them that I thought I would share with you.
First, if you are looking for them, they can be found in your Resource Kit. If you have installed this kit on your Server, you will find them in the Program Files\Resource Kit\SMS\Diagnose directory. I believe they have a DLL that they both depend on which will need to be copied to the machine that you are running the utilities on.
These utilities are used to add system records to your SMS server. In fact, they generate DDRs that are fed into the database and will eventually (whatever that means) show up as systems in your "All Systems" discovery records. I have used them when I lack the patience to wait through the time cycles that SMS drags me through.
You must run these utilities from the Site server, which results in something peculiar -- this system will be discovered as a NT server (or whatever you are running from).
When you see the following message, "The DDR has just been sent to the Site System", you will not immediately see this machine in the discovered list; it will take some time.
From here, you will have the freedom to manipulate those systems and create your own collections.
There are a few variables that you have the freedom of entering, but the only one that you have to put in is the system name.
The command line version (addsystem.exe) has specific syntax that you will have to use, but you can get that from the program itself.
Other than these points, I have found that these utilities (like most of the resource kit utilities) have proven to be pretty useful. Remember that, when working with SMS and any of its components, don't expect anything to happen immediately.