Elwinna,
I believe much of your problem was a loss of resouces.
Rebooting a computer from time to time especially when using Windows ME and XP, "reclaims" memory that is being tied up within the system. Since you said you "hardly" ever reboot seems to explain why it clears up from time to time.
Normally, when the computer no longer needs memory, it should return it to the "bank" for re-use.
Sometimes this does not occur and if you keep using the computer, your memory will get so low, that any function could freeze it up.
This is called "leakage" and occurs more frequently in ME systems than others.
Defragnentation and a Diskscan as part of a regular maintenance routine will keep problems to a minimum.
Good luck.
PS: You mentioned a "dirty" word...Norton!

It is not as easy to remove completely as you might think.
If you continue to experience trouble, then we must do an indepth removal procedure for Norton. You can search the forum for many many posts on Norton removal.