A friend used my computer to access her Facebook. Now whenever I open Facebook, it assumes I am she. I cannot access my own.
PrivaZer delete all files on computer.
Since your friend accessed her Facebook account on your computer, wouldn't it have been easier to ask her how she did it.
Delete the cookies and browsing history
as you are using Internet Explorer 9
Press CTRL +SHIFT +DELETE
which will open a window for deleting cookies tick all boxes and press ok
after deleting browsing history go to start and search in the bottom box disk clean up
you will get disk clean up in the programs section open and clean up
try with another browser and if it is the same thing then the problem can be more complex.
Just press Ctrl+Shift+Delete and uncheck all boxes except of 'Cookies and websites data' and press Delete. You're done.
Clear your cookies and cache, that will remedy the problem as I had much the same thing. The best way to clear out the cookies and cache is with CCleaner or Privazer
This issue is common when the cookies are not cleared between users. Rajaa's suggestion will work, or download and use CCleaner (cleans out a lot of junk and may increase the performance of your computer). http://www.piriform.com/ccleaner
Open IE9 then click on the gear symbol on the right hand topside. Then click on internet options, then under browsing history, click on delete, tick on all the options and then again click on the delete. After that try once again.