The warranty I'm referring to is one that may have been provided by the "refurbisher" that the OP bought the system from, not the one from the factory. Most such sellers will guarantee a system's performance as long as you don't start taking it apart. I myself have done this with some laptop sales (putting custom tamper-proof stickers across the removable panels, for instance).
Even though the OP reports the system having Windows 7 already installed on it, with the possibility that it does already have some software that can ID the memory slot usage or that some software could be easily downloaded, installed and interpreted, I'd still suggest getting a copy of memtest86+. For most recent systems, you can get information on the slot usage like this:
Here on my T410, you can see that both slots are occupied by 2GB Samsung modules, with the speed rating and part number clearly noted. I'd consider this information a "bonus" in that the original purpose of memtest86+ is to verify that the memory is fully functional. Note that this information comes from the SPD (Serial Presence Detect) memory that is installed on each module. Each module manufacturer is supposed to properly identify what it is. I'd be somewhat surprised if this information comes back incorrect. About the only thing I can think of is some shady memory dealer that is selling counterfeit modules and they program the SPD info wrong. That in itself would probably lead to the module not working with the system in the first place but stranger things have happened.