If I go into "msconfig" and delete stuff.............?

1) If I go into "msconfig" and 'start up' and delete stuff.............

Will I have the option to re-add it later if I change my mind?

(I'm scared that I will delete something that I need)

I'm hoping I can re-tick stuff at a later point, that it doesn't get wiped off forever, if I un-tick the boxes now.

(I have 25 ticked things now, presumably that's why my pc is so damn slow)

Question 2) Will deleting stuff in here help with the general running of my pc, or only on start up, because my pc runs slow all the time, not just on start up.......

Is there anything else I need to do to get rid of programs running in the background.

(I know about Add/Delete Programs and I know about defragging and cleaning disk and I know about having an anti-spyware program, but any other tips would be helpful. I have lots of free memory on my pc, but it runs slow for other reasons - ie too much going on in background I assume)

THANK YOU SO MUCH FOR YOUR HELP. I SINCERELY APPRECIATE IT!!!!!!!

If I go into "msconfig" and delete stuff.............?internet security 2006

Yes, you can go back into it and re-check things if you want, it won't delete anything.

And it will help at startup and should also help while the computer is running because all those things you uncheck usually run at startup and continue to run while using the computer.