Hi there and welcome to BC!
There is a great tutorial found here
, which i've recommended to people before. It even has pictures so it should be quite easy to follow. There is a set way of deleting an account through the control panel - deleting the specific folders would not remove the account and would most likely bring about a handful of other problems down the line. That's how to delete the account.
You say that you can't view the tab of the user you wish to delete - when you boot and get to the log-in screen can you see these users listed?