+1 I work at an office store and see this everyday.
Why buy a new desktop when you don't have to?
Desktop computers (whether in a business, even a small business, or in a home) tend to get upgraded last for the very understandable reason that you CAN upgrade *piecemeal* - you don't have to upgrade the entire contents of the case. (Even those much-maligned HP/Dell/Lenovo/etc. desktop PCs can, more often than not, be upgraded, albeit with varying degrees of difficulty compared to more ordinary desktops - still, it can be done.)
My current PC (which I built) is a case in point - the entirety of its hardware can be seen as *dead hardware*.
CPU - Intel Core 2 Quad Q6600 (Kentsfield) - dead four years.
Motherboard - ASUS P5G41-M LX2/GB - Likewise, dead four years.
GPU - nVidia GeForce GTX 550 Ti (factory refurbished) - Dead two years. (It replaced a Visiontek AMD HD5450 iSilence - itself dead three years.)
HDD - WD Caviar Green WD10EADS (1TB SATA 3.0-g) - Dead two years.
Yet this collection of dead hardware runs four operating systems (Windows 8.1, Windows Server 2012R2, OS X 10.8.4 and OS X 10.9 DP2) - all of which are current, if not bleeding-edge.
I can do anything I could care to on this same collection of dead hardware - including current gaming. (I was playing RIFT earlier today - fully maxed out at 1920x1080 with all the eye-candy turned all the way up. And again - this is on *dead hardware*.)
Further evidence - my 3DMark (current) results. http://www.3dmark.com/3dm/914572