How could someone turn off my yahoo messenger from a different computer?

I do not use any messenger program, and have avoided having any messenger program installed on my computer. Now, Yahoo has piggybacked a messenger onto Yahoo Mail and apparently posted my identity on a directory somewhere because I am getting spam. I...

Someone broke my car window and stole my computer a while back. The Yahoo Messenger on that computer automatically logs in when you turn on the computer. The person who stole my computer still uses that screen name I used and it notifies me when they...

I used to be able to just turn off my computer and yahoo messenger signs out on its own, so i don't have to be bothered with signing it out myself. i changed PCs and now my yahoo messenger doesn't sign out unless i sign out, which is a pain since i share...

basically i now how to turn it on, and allow someone to access it without permition, but how do i set it up to automatically start broadcasting webcam when the yahoo messenger automatically starts when my laptop turns on, is there a setting for this...

I keep going to preferences and connection and removing it and unchecking the two boxes and the 'remember me' and signing out, but when I turn yahoo messenger back on, there it is again. Someone else uses my computer and I found out they are also using...

In the earlier version of yahoo messenger ( I do not know 8 or 9 ) when i am chatting with someone on instant messenger I could go to actions and then use the option call computer. then I could voice chat. also there was a symbol for web cam which i...

when i tried downloading it showed 100%, but never completed but smiley appeared on desktop. whenever 100% shown it would not let me out after i patiently waited too see if it finished. i would have to manually turn off computer and restart. yahoo messenger...

I can see other people cam fine but when I invite them to see my cam in yahoo messenger it Locks up my computer and I have to turn it off and then back on to unlock it. Can someone help me please so others can see my cam?

Well this is a several part question.The first part is whether it's possible for someone to hack into your computer if you are chatting with them on Yahoo Messenger? If so What kind of hacks can they use and what can they do on your computer? Finally...