A guest account allows people to have temporary access to your computer. People using the guest account have only limited access to resources in Windows 7. Although they have only limited access, it is always good that you take care of all security aspects when you create the guest account. By default guest account is disabled on Windows 7, but you can enable it easily using the control panel.
Control Panel->User Accounts and Family Safety->User Accounts->Manage Accounts. Click on the guest account to enable it. The guest account by default does not have a password, but you can set a default password to prevent any unauthorized access. To set a guest account password, open command prompt with administrator privileges and type “Net user guest password” without the quotes. Here password set is “password”.
Guest account should never be accessible over the network as they are meant to be used for local system. You need to make sure that guest accounts are not accessible over the network. Open security policies (Run-> secpol.msc and press enter). Navigate to Local Policies- User Rights Policy. Here make sure that “Deny access to this computer from network” option has guest listed.
You can also make sure that guest account does not have option to shut down the computer. This can be again checked through security policies. Navigate to Local Policies- User Rights Policy. Under the settings “Shutdown the system”, make sure that guest account is not listed.
These steps should make your guest account secure and prevent unauthorized access.