Computer advice -- what features do I need?

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I need to buy a new home computer, my PII 450 running Windows 98 just died and rather than spend money to fix it I figure I will just buy a new one. If anyone can help me decide on some specifications I would appreciate it.

Uses will be:

Web surfing
rarely word processing
perhaps the occasional game, maybe counterstrike

Questions are:

Choice of operating system: Windows XP Pro vs. Windows XP home
choice of CPU
type and amount of memory needed, I don't understand the different kinds of RAM/speeds of RAM/bus speed etc.
other features needed

Looking over the choices between different computers I am not sure what I need, I want a machine that will last me for the next 5 to 10 years. I don't want to save money on a cheap computer that will cost me more to upgrade later.

Thanks for any advice.