I had my friendly geek put the fastest possible controller in here, still compatible with WinXP -- and as much memory as he could stuff in the tower; I think I have 32 gig and that made a HUGE difference in the speed at which things load, particularly the heavily graphic stuff on Facebook games
fortunately the computer was built up, originally, by the computer dept at MCC, so all components are "standard" rather than brand-specific, making it far easier and cheaper to update .. but I think I've now hit the possible ceiling for this operating system -- and for several good reasons I will NOT change that on the tower (though our laptop runs Win 7)
adding memory to laptops is a bit different, since almost all of those require brand-specific memory modules
If you have A 32-bit processor, it can only address 2^32 (2 to the 32nd power, or 4,294,967,295) addresses in memory, so that places a 4GB limit of RAM. Other hardware devices claim some of that memory for their use, which takes away what is available to the OS (which also claims some RAM) and applications. Typically this leaves you with about 3.2GB of RAM left for applications.
So, if your guy has put in more than that you have really overspent! (Unless you have a 64 bit processor, and that's another story!)