Mostly they are started via the Startup group (Start/All Programs/Startup), others get added to the services list. There are a few apps that will allow you to change what gets started, but if it shows up in the system tray it should be configurable to not automatically run. Google msconfig for proper use - it will do the trick for what gets started at boot time.
In my experience a fragmented disk will have more bearing on performance than memory resident programs.
It's also important to have your swap file properly configured for optimum performance. Rule of thumb is swap file size = 1.5 times the amount of RAM. If you have 1gig of RAM, you should have your swap file size be 1.5gig.
Thanks for the help.
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