Valve want to know what you've got installed
Just like they started asking a selection of gamers for permission to scan their hardware, Valve are gearing up to pop round and politely ask you for the go-ahead to have a gander at your installed programs.
To have a glance at what they're looking for, open up explorer in Windows 7 and paste this into the address bar:
Control Panel\Programs\Programs and Features
I really don't mind showing Valve my hardware so they know, for example, whether or not to look into supporting the type of processor I have or maintaining DirectX 8 support in TF2, but what sort of useful information can Valve glean from my installed programs list, and how does that benefit me as a gamer? It's possible they want to know how much of my RAM is taken up by miscellaneous crap. What do you reckon?