try running CCCleaner, it cleans up the registrey which could speed up your computer a little.
As for Mac's...i'm a mac user and i've had my laptop for awhile now...and it hasn't slowed down on me yet...i use it for various things...downloading, surfing, school, videos, etc...and it still performs as fast as it did out of the box
Desktop - DualBoot: Fedora 15/Windows 7 64bit
Netbook - Windows 7 Professional
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