press ctrl,alt and delete and select ,start task manager, when task manager opens click the new task button, then in the window that opens type explore.exe,
that should get the task bar back,
if that fails then open task manager again go to processes and scroll to explorer.exe and then press end process.
then repeat the steps above with the new task /explorer.exe.
let us know if it works
edit: chances are if you have logged off or rebooted since then it will have returned.