XP Task Manager - End Process

Using XP SP 3 - (up to date) In trying to track down hidden background activity hogging my CPU, I hope to go through Task Manager and terminate various processes to assess the impact on performance. After five years I have accumulated about one hundred processes - and guess that many of these are bloatware from arrogant applications. If I select "end process" - does this get re-instated at the next boot-up, or is it removed from the Start up list ? I am aware of the risks of ending some essential services - I hope to be be able to identify these in advance. Many thanks Philip

Task Manager only manages (sort of) tasks that are currently running. It does not change how they were loaded/started.

I am aware of the risks of ending some essential services

The only real risk of terminating any task or service via TM is your current session will crash, but all will be restored upon reboot.

You can check your Startup folder under the Start button and remove the shortcuts. That does not uninstall the programs, it just means they will not start with Windows.

I recommend you work your way through your installed programs from the Control Panel applet, and uninstall those you don't use.

How does it behave if you boot to Safe Mode with Networking? If better then something is starting at boot that is causing the problem.

Advanced startup options - XP
Advanced startup options - Vista
Advanced startup options - Windows 7

Use msconfig to determine what is causing the problem

These are good tutorials on using msconfig in XP, Vista or Windows 7:
How to use msconfig in Windows XP
How to use msconfig in Windows Vista
How to use msconfig in Windows 7 and Windows 8

Click on Start then Run, type msconfig and press Enter.
Click on the Startup tab (for Windows 8, the Startup tab has a link to open Task Manager/Startup tab. Use that.), record what is currently starting then click the Disable All button.
Reboot and see if it runs better.
If yes then use msconfig to enable several items at a time till you find the culprit.

If no, start msconfig and click on the Services tab.
Check the Hide All Microsoft Services box, record what is currently starting then click the Disable All button.
Again, do a regular boot, see if it runs normal.
If yes then use msconfig to enable services till you find the culprit.

Once you've found the culprit, uninstall it or find out how to eliminate it from your system. Simply disabling it in msconfig is a temporary fix at best.
Enable everything else you disabled.