CYB2K.EXE<--------Cybersitter, it's a program that monitor your internet usage and prevent user from accessing porn website, this may be the software that disable the task manager so that you can't terminate it.
Type gpedit.msc in run, Go to User Configuration/Administrative Templates/System/Ctrl+Alt+Del
Remove Task Manager is the setting you want to not defined or disable if its enable you wont be able to access it.
Go to /Start Menu and Taskbar/ nothing should be enable, everything should be set to not defined, theres a couple of setting you want to check, anything with the word taskbar or disable that is relevant.