If you use Window XP (and I would imagine Vista), you can set up a separate User Account.
User accounts personalize Windows for each person who is sharing a computer. You can choose your own account name, picture, and password, and choose other settings that will apply only to you. A user account gives you a personalized view of your own files, a list of favorite Web sites, and a list of recently visited Web pages. With a user account, documents you create or save are stored in your own My Documents folder, separate from the documents of others who also use the computer.
If you use a password for your user account, all of your files are kept secure and private so that other users cannot see them. However, you can still mark certain items as shared if you want other people to be able to access them. If you do not use a password for your user account, other people will have access to your account and be able to see all of your folders and files.
If you have a user account and you change computer settings, such as the type size or the screen saver, those settings will apply only to your account.
As a user with a computer administrator account, you can create, delete, and change all user accounts on the computer. You can create as many accounts on the computer as you want, and have full access to all accounts on the computer. For information about the types of accounts available.
You could even have a separate browser that is only accessable to your account, so all your history, bookmarks, etc. can be kept private.
