Computer games on Steam

Steam is a really nifty delivery mechanism, and a lot of older games are moving over there...just this past week, the entire Quake collection was available for $15. Hard to beat that...

Except that all too often, you can buy a game that literally WILL NOT PLAY. Is Valve actually testing any of this stuff?

I'm running Win7 x64, and I have some serious trouble with things. I have had several demos fail to run, and a couple of things I've bought also would not run. I think a couple of demos have even failed to install.

Surely it doesn't take an Advanced Degree(tm) to figure this out? At the least, the Steam client should be able to detect your machine properties and tell you that it won't run certain things.