Built in 2009, hardware cost: about $900 originally.
Currently:
Gigabyte X58/1366 socket (can't remember the exact model now)
Processor: Core i7 920 (Bloomfield) -- runs stock speed but is undervolted to 1.005v
6 GB DDR3/1600 running in tri-channel configuration
Geforce GTX 670 graphics card (this is actually an upgrade for me from January)
WD Caviar Black - 1 TB -- Boot Drive
Storage drives
WD Caviar Black - 640 GB (this was the original boot drive when I built it)
Samsung - 1 TB
Seagate - 2 TB
Optical drives:
Lite-On DVD burner w. Lightscribe support
Pioneer BD burner
OS: Currently Windows 8.1, originally Windows XP x64
Case: Antec Nine-Hundred
Power Supply: Antec TPQ-850
Monitor: Samsung T240HD (this is a 1920x1200 monitor with TV tuner functionality and component vid inputs) (separate purchase)
I'm not much of a gamer, and the system was built for my hobby of video processing/encoding, so I focused on putting money in the CPU and graphics were less important. I only had the one smaller Caviar and the DVD burner. But as HD video becomes more popular, storage needs grew. I do play games occasionally and have an account on Steam, I originally had a Radeon HD4830/512 for the graphics card and it worked fine. I had to upgrade recently because of the high video processing requirements of MadVR and a friend gifted me a copy of Transistor last Christmas (the system requirements needed a card with at least 1 GB of VRAM). I actually bought the GeForce second-hand from the same friend for a good price (it's an RMA replacement he'd only used for a few months himself before upgrading to a GTX 970).
I might build a new rig this year. I don't really have a processing emergency or anything, but I want to see what Skylake offers. I'd like a system that isn't so large and runs cooler. I have an NCASE M1 in a box here for the next system when I do it, and I already have a small FreeNAS server running I want to transition all the video storage to in the future so I don't need all the spinning drives in the PC. Will likely go to an SSD and 16 GB RAM for the next build.