You can't create power users in XP Home, but since you're using Pro, this isn't a problem. A power user has more rights than a limited user, but not as much power as an administrator. Here's how to create a power user account.
Go to Control Panel > User Accounts, and click Create New Account.
When you pick an account type, choose Limited.
Right-click My Computer and choose Manage.
Cascade out the Local Users & Groups folder, Users folder, and open your new account.
In the Member tab, add the user to the Power Users group by typing "Power User" (without quotation marks) in the Group Name field.