I know these forums are not specifically designed for Windows problems, but I have had such good experiences in the past, I thought I'd give it a go.
I wanted to switch users a few days ago, but when I clicked the start button and clicked the arrow next to shutdown, it says lock, log off, restart, or sleep. The switch user option used to be at the top.
I have tried going into the registry and finding HideFastUserSwitching, which I had to create a DWORD value for, because it wasn't there - needless to say that didn't work.
I was told to also enable the Fast User Switching service in service.msc, but it wasn't on the list.
I have tried going to task manager and clicking the 'users' tab which miraculously disappeared - replaced by a TCP/IP tab.
I don't know what else to do apart from re-install Windows!
look under system..system settings user accounts. make sure there still the main admin account and the temp .net account there. if there is and there no other account there then make a new account there. you should then be able to switch to the new account without issues. if you dont own the pc or go a virus and your not the admin you wont be able to make a new account.