I have two PCs in my house, neither of which are used for gaming. I was a PC gamer in the mid 90's, but soon went back to consoles.
My office PC is my work machine for doing web and graphic design freelance, video editing, etc. It's a 2008 model Gateway running Vista, an AMD quad-core, 8GB DDR2 ram, and 2.75TB of storage. 750MB on the C: drive and 2TB on my media storage drive. It also fills the role of media server for our home, where we store TV shows, movies, music, etc.
Our HTPC is in the living room and serves as our entertainment center. We ditched cable 3 years ago and went all streaming for our entertainment. This machine is a Dell Zino HD. Nothing fancy in the specs department, Windows 7, but it does what we need it to do. We use it to run XBMC to access our media server, and Windows Media Center serves as our DVR to record over-the-air TV. We added a wireless keyboard with built-in trackball, so we can browse the web from our couch too. We love this setup far more than what we had with cable.
And by dropping cable we've saved about $3,000 since we went to this system and honestly, we prefer it. Cable was replaced by Netflix, Hulu and other streaming sources like YouTube and Revision3.