Giving a password to the 'Guest' user account
Windows XP contains a guest account (turned off by default in XP Pro) that has the rather unique distinction of not having a password. Not only does the account not have a password, you can't even set one. As you can see, if this account is active, it presents a slight security risk. Fortunately, there is an easy way to assign a password to the guest account:
To apply a Password to the guest account:
Using an account with administrative privileges, go to the command prompt ('start\run' then type 'cmd') and enter the following command:
'Net user guest password'
Now go to 'start\control panel\user accounts' and activate the guest account if it is not already. You will be able to assign and change its password.