ok, that's a start.
The spec page from the service manual for the 3000 is here:http://support.dell.com/support/edocs/syst...s.htm#wp1075776
It shows the choices of processor run from p4 3.2 to celeron 2.8
These are slow by modern standards but not to bad for the times. If you experience freezes, stuttering sound or video, you can pull up task manager, go to processes, and click the top of the cpu column until the processes are in order of cpu usage. This can tell you if some single process is hogging the cpu.
This model did not ship with a full complement of memory unless it was ordered with it. Do you know how much ram you have? What your virtual memory settings are? Those can make a world of difference in speed of program execution.
Have you checked your dsl speed lately? Perceived speed issues while online can contribute to an overall feeling of "slow". http://www.speakeasy.net/speedtest/
So I am guessing from your post that you feel the startup speed is an issue?
Actually uninstalling some of those items rather than blocking them from starting might be the next test.