This account is one huge security flaw when it comes to windows operating systems and removing this account is no easy task, In Windows Vista it’s easy to disable the account however if you’re not happy with just disabling the account there is more you can do.
You can set a password for this account which will make it much more secure then it was before and doing so is very easy as I’ll show you below. You are not able to set a password for the guest account in user accounts! Blame Microsoft not me 
(We are going to use the Command Prompt to set a password)
Click Start (Vista Logo) ->All Programs -> Accessories -> Command Prompt
Or
Hold down the windows Key pres R and then type in Cmd and press enter
Now we have a Command Prompt open.
The rest is very simple you are going to enter net user guest and your chosen password after that.
net user guest password
Just change password with your actual password and press enter.
It’s really that simple, now if you want to check that the guest is really now password protected just to and look in user accounts:
Start (Vista Logo) -> Control Panel -> User Accounts -> Manage Another Account
If your guest account is turned off, to see that it is now password protected you’ll have to turn it on for a moment, and you will see under guest account it says Password Protected.
Hope this Helped you
