When you log into Skype through the application it will create a profile on that computer. If you use another persons computer to log on even after you log out that profile will still be there.
To Delete the profile:
1) Close Sype
2) Click Start. Type in "run" in "Search programs and files". Click on run.
3) Run "%appdata%\Skype"
4) Find the folder with your username and delete it.
5) Restart Skype.