There are three posibilities to prevent user action on taskbar:
1. Switch-off task by delete registry value under [HKLM]\Init for start explore.exe
2. Hide taskbar by your own application, e.g. in C++ use:
CWnd *pTaskBar;
pTaskBar = FindWindow(_T("HHTaskBar"),NULL);
pTaskBar->ShowWindow(SW_HIDE);
3. Set taskbar attribute "Auto Hide" and disable attibute "Always on Top" (by right click on none icon area on taskbar ... )