I have the box checked in Messenger, "General to Automatically start Yahoo! Messenger", but it still does not start auotomaticaly. My default Browser is Firefox, but I tried making IE the default, and it still does not work. I also changed the Messender connections to all 4 options and it still does not startup.
Answers:
Go to Start, then run, type msconfig, click ok, select the startup tab. Check the programs you want to run when your computer starts up and uncheck the ones you do want to run. Programs that are check to run are always running when computer is turned on, too many programs running at the same time can slow your system down.
It sounds to me like you are haveing a probs with your windows instalation and/or is your pc full of spyware!
Try to download spybot and run it on your comp and if it still doesnt work then format your hd and put a fresh instalation of OS.