How can I prevent Skype from starting automatically on boot?

My girlfriend logged into her Skype account from my Xubuntu 12.10 netbook, and ever since then Skype starts automatically every time I boot. How do I prevent this from happening?

Things I've tried:

• Removing it from the Settings Manager->Session and Startup->Application Autostart - couldn't find it in the list.
• Checking for a relevant setting in Skype itself - couldn't find anything of the sort. (I remember there was a similar Skype setting somewhere whenever I've used it on Windows. Considering my girlfriend is a Windows user, could it be that this is a setting that's available on the Windows client but not on the Linux one, and somehow got transferred?)
• Using BUM to turn it off - again, couldn't find it in the list.
• Uninstalling Skype with apt-get remove skype --purge and hoping that it removes all the settings as well - it didn't.

Save for reinstalling, what else can I try?

While on the same note - how is it possible for Skype to autostart without going through the normal Upstart route?

EDIT: Couple of more things I tried:

• Looking for anything similar in Skype support - I didn't expect to find anything, and I didn't.
• Looking through the .Skype folder in my home directory. I did find a couple of files which looked promising (.Skype/shared.xml, .Skype/[my username]/config.xml, .Skype/[girlfriend's username]/config.xml), but looking through them didn't yield anything. Plenty of SQLite files though. Could it be that this setting is somewhere within?

For the new 2017 version of skype that's impudent enough to add itself to autostart each time it's started (seriously? Never installing it on my own machine) it's enough to create a folder with the same name as a file it's trying to create:

rm ~/.config/autostart/skypeforlinux.desktop
mkdir ~/.config/autostart/skypeforlinux.desktop

Since it seems the answers here change all the time, as of an install of skypeforlinux from earlier this week (version 8.11.0.4), I managed to get the autostart to cease with two steps.

First, open up Skype, go to Tools > Settings and uncheck "Automatically start Skype".

Then, inspired by azeam's suggestion, go to (Xubuntu) Settings > Sessions and Startup > Application Autostart, and remove the item for Skype. I'm not sure if unchecking works; I tried that first, but it may have conflicted with Skype's internal settings when I tried it.

Had the same problem and the following seems to have taken care of it: go to (Xubuntu) Settings > Sessions and Startup > Session, find Skype and left click where it says "If Running" and change it to "Never".

I had this same issue. I was able to prevent it from starting automatically by removing skypeforlinux.desktop from ~/.config/autostart/. I'm using lubuntu; the location of your autostart folder may vary. You can find by using:

$ locate skypeforlinux.desktop

You'll really only want to delete the copy in the directory called autostart, otherwise you won't be able to start the app from the icon.

I'm assuming that the next time you actually, intentionally run Skype (I hope, for the sake of your sanity, that this day is far in the future) that it will try to put that file back. In which case you might have to delete it again or scour Skype for the setting that will prevent that behavior.

Go to Tools -> Options -> General settings. Uncheck the option "Start Skype when I start". Save and Quit Skype.