Short answer
Yes, it would be very unwise.

Long answer
"I feel that I am properly protected without it". What do you base these feelings on? Do you base it on research that you have done that...

Read crunchie's last post. Start your own thread.

If you have a pirated version of Windows (or your system fails the genuine Microsoft Windows test for whatever reason), you cannot download the program.

Have you tried running all the scans from Safe Mode (http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx)?

Go to the guide that I have linked to in the bottom of my sig. Follow the optimize guide which will find and fix most any problem that your computer might have due to badly behaving software.