why not?
is it greyed out or something?
To turn the guest account on or off
A guest account provides access to the computer for any user who does not
have a user account on the computer.
The steps to perform this task differ depending on whether your computer is
a member of a network domain or is part of a workgroup (or is a stand-alone
computer).
My computer is on a domain
You must be logged on as an administrator or a member of the Administrators
group to activate or disable the guest account.
For information about activating or deactivating the guest account using
Computer Management, click To disable or activate a user account.
My computer is not on a domain
You must have a computer administrator account on the computer to turn on
and turn off the guest account on the computer.
Open User Accounts in Control Panel.
Click Guest.
Do one of the following:
To turn on the guest account, click Turn On the Guest Account.
The guest account will be activated. Now, a user without a user account on
the computer can log on to the computer at the Welcome screen.
To turn off the guest account, click Turn off the guest account.
The guest account will be deactivated. Now, users without a user account on
the computer will not be able to log on to the computer.
Notes
To open User Accounts, click Start, click Control Panel, and then click User
Accounts.
Users who log on to the computer using the guest account do not have access
to password-protected files, folders, and settings.
For more information about user accounts, click Related Topics.