Mainly: web surfing, news, word processing. Occasionally: playing MP3s, watching DVDs, watching streaming online video, LEGALLY downloading an app/MP3/video, encoding video, gaming. Rarely: powerpoint, Excel, ripping/burning CDs.
Ever since I built a dedicated HTPC for recording and playing back television, I haven't had a need for highend hardware. My main computer now is an undervolted Celeron 420 at stock 1.6GHz, 120GB hard drive, Nvidia IGP, 1GB ram, Windows XP, and CDRW/DVD-rom combo drive. It's all I need.
My HTPC is an AM2 Sempron LE-1100 undervolted and mildly overclocked to 2.0GHz/1.1 volt max, 850MHz/0.8volt idle. 200GB hard drive, 1GB dual channel ram, ATI x300SE graphics card, PVR-250 dual tuner card, Windows MCE 2005, DVDRW drive. Jetway nvidia 6100-405 motherboard.
I would like to see the overkill hardware specs for the 75% of people above me that do jack on their computers. Perhaps you guys should run Task Manager minimized to system tray 24/7 like I do, then it might become apparent just how little of system resources are being used.