Arrrgg! Can't uninstall Defender Pro

I'm definitely in foreign territory here. Never posted on a site like this before. Sorry to say, I am only a major geek wannabe. I borrowed Defender Pro from a friend and installed it to protect my computer but now I'm having trouble opening my gmail. I went to see what processes were running when it wouldn't open and it was only mozilla and a program called avz.exe associated with Defender Pro. When I went online to research avz.exe I learned that Defender Pro is considered by many to be a terrible program and wreaks havoc on your computer... really a malware program itself! I'm trying to uninstall and it's giving me an error message that says "error 1921"... "you must verify that you have the authority to remove this program". After more searching it turns out that many have had issues with uninstalling/removing this software. I came to your website to get the download some freeware to uninstall but then I read that some people had the experience that it uninstalled too many items on their registry and I can't take the chance that my laptop would be unusable (almost done with my dissertation that is due in one month). [Windows XP] Please help.