Ubuntu – How to 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?