How to install Windows XP without anyone changing the existing OS

Though you can install Windows XP or any other operating system as a second OS on your computer, you still cannot protect your fi les from another person accessing the fi les on your primary OS partition. There are ways that he/she can access your important fi les. If you want to protect your fi les and settings from the other user, I would advise you to create a user profile which is a standard user instead of a user with Admin rights. This will create a different account for the user and limit the areas he/she can access. The only other way you can keep the other user from getting into your data is to install another hard drive with an operating system on it for the other person to use while disabling your main hard drive from the system BIOS. You would have to go through the trouble of enabling and disabling the drives from the BIOS every time you or the other person uses the computer. Alternatively, use encryption software such as TrueCrypt.