My system serves as 2 things: Gaming system first and foremost (set it up that way from the instant I first put it all together) and secondly, a wordprocessor, video playback (avi,mpg,wmv,etc), graphic editor (through PSP7.0), stereo (Sound card runs through my stereo to play CDs and, shield your eyes!, MP3s), and the occasional CD burning/copying and powerpoint presentation.
Since I first put this machine together, I have had one problem that has become one of those 2nd nature things (like taking vitamins in the morning) - and that is that my joystick can't be left in the USB port when I power down the PC and must be plugged back in (also must nuke the USB port). Other than that, its stable and I've never encountered non-user errors or problems.
I do regular maintenance on the PC hardware - cleaning dust off the hardware and fans/heatsinks, making sure all debri is out of the way for optimum airflow through the case - and software - fully removing entries for programs after deleting them, scandisk atleast once a week, defrag every month or 2, completely removing all evidence of prior hardware (which is really only the video card) driver/installation, and a few other things I can't remember off the top of my head. I only put in this much effort to keep the system running its best so I can put games at max details and recieve decent/fluid framerates.
-SW