One simple thing to try is going to Start>Run>msconfig and disable all the unnecessary startup applications. Should be a tab in there called Startup. Just start unchecking. You'll notice a difference especially on an emachine. If youve tried any of those freeware programs that claim to optimize your computer's speed, remove them asap.

You can try Ccleaner and start cleaning out all your old registry entries, and you can run a system cleaner too in that app too. Ccleaner (crapcleaner) is the only program of this kind that I'll recommend.

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1985 CA 300D Turbo , 213K mi