Removing the shutdown option from start menu in your computer:

Click on start>run(win key+r)

Then tpye "regedit" there, this opens up the registry editor, now goto

HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows>CurrentVersion>Explorer

Then set "NoClose"="DWORD:1?

+

Hive: HKEY_CURRENT_USER
Key: Software\ Microsoft\ Windows\ CurrentVersion\ Policies\ Explorer
Name: NoClose
Type: REG_DWORD
Value: 1

Also if you would like to remove the shutdown button from the login screen:

Hive: HKEY_LOCAL MACHINE
Key: SOFTWARE\ Microsoft\ Windows\ CurrentVersion\ policies\ system
Name: ShutdownWithoutLogon
Type: REG_DWORD
Value: 0