As you may (or may not) have found out, "Additional Guard" is a rogue anti-spyware program. See the following removal guide:
Remove Additional Guard (Uninstall Guide)
NOTE: Step #3 instructs you to download (and run) rkill.com. There are three other versions of Rkill, which have different extensions. Try the one suggested in the guide. If it doesn't run, try the second. IF one DOES work for you (immediately) run a Quick Scan with MBAM. Instructions for installing Malwarebytes' Anti-Malware are within the guide.
If Rkill doesn't help, give the below a try. :
Follow ALL the steps and instructions in the removal guide.
Best of luck..
I was trying to install new internet security software and got the message that 'Additional Guard' was on my pc. After researching, I downloaded Spyware Doctor. When I try to open Spyware, nothing happens. PC has Windows XP, plenty of room on the hard drive.