You need to have admin rights to install software on your computer. You do not need admin rights to run the software. So most of the time you can run in user mode.
Most viruses and malware need admin rights to install on your computer. So if you run in user mode the virus can not install. My garage computer runs in user mode with no added virus protection and I have not gotten a virus in over five years. I never open e-mails from unknown people with this computer.
How to create user accounts.
http://www.bleepingcomputer.com/tutorials/create-new-user-account-in-windows-vista-7/
I will look for a more complete answer and post a link.
Thanks for the insight Thomas Thomas...