I've been into gaming computers since Windows 95 and Quake 1 and "GLQuake" came out and I purchased the very first 3DFx Voodoo graphics card and started "upgrading" my computer. Pentium 166 days and dial up modem days.
Since then...have feverishly been into gaming...FPS games. Always built my own custom gaming rigs, got huge into overclocking. Used to build gaming computers for friends too..and started doing a bit of a side business building gaming computers. Being very involved with large organized LAN parties at hotel convention centers and places like that...got a bit of business through that.
Stopped building gaming computers on the side about the time Pentium 4's just came out...but kept building them for myself, and for the boy since he got into the age to start getting big time into online FPS games.
Have also built higher end video editing machines for clients that did video editing for a business. Recent one...24 gigs of RAM, 4x WD Black Edition 64 meg cache 1TB drives, quad core i7, Asus mobo, ATI Radeon something card.
As for my clients..business clients...I also have a few clients that are architects, or engineering/design jobs...running CAD software like Solidworks. I don't build computers for business clients....always use Tier-1 products for their computers. I do strongly urge them to use proper "ISV certified graphics workstations" for those computers that run design software. Example...Dell Precision workstations with higher end hard drives, processors, and graphics cards such as nVidia Quaddro or FireGL cards.