Software specs
"Fair enough, but shouldn’t a PC gamer know their machine’s specifications and then match these up to the system requirements listed on the game’s box?"
That depends on whether the "minimum specs" are genuinely based on requirements for the thing to run at all, or merely represent what someone putting together the box art thinks sounds like a likely spec of an average PC within the last 2-3 years.
I run a machine elements of which are on the ancient side (GF3Ti200 and an Athlon 850). I regard even the minimum specs on the box as suspect - my machine chugs along with Doom 3 happily whilst miles below the official specs and handled Prey without issue but won't touch Quake 4 as it specifically needs SSE (which the old Althlon lacks) - the QIV specs don't mention this, they just demand a P4 class or above (even though it would probably run fine on a P3). I understand that companies can't test their software with every feasible hardware combination but the information provided isn't enough to make an informed judgement - its frustrating knowing that on the offchance that your purchase won't work you're potentially out of luck "because you don't meet the published specs".
(I'm not a hardcore gamer and the machine works very well for its main role as a family PC/ PVR - it'll get replaced when it dies)
With hardware purchases its even sillier as you are very unlikely to need a 2GHz+ machine to install a new DVD burner or printer successfully... but it still gives the reatiler a get-out clause should it not work.