To provide basic functionality to a user who just needs web surfing, a little
word processing, and the occasional game of solitaire, its important not to go
overboard. Such a user has no need for a top of the line processor or 3D graphics
card. A modestly configured system with an adequate internet connection will
suit this user best and can be assembled quite cheaply.
This usage pattern is not going to stress any particular component, you
should be looking at a mid- to low-level processor (historically, and currently,
at about the 110 ($200 approx.) price point or less), enough RAM for the OS
and a mother board with built in Ethernet, video and audio. You can use a
mid-level case/power supply combo (these components are often sold as a pair).
If you have a little extra money, spend it on a better monitor, mouse/keyboard,
and case/power supply in that order.