Well,

If you were in Windows - you would look for the "uninstall" program - or - in some cases the install program realizes that you already installed it ( as in M$ Office 2000 ) and changes to a "update or remove" switch...

But, since we are in Linux - hopefully you used apt-get install guarddog" -=- in which case you would do the following to remove it -=- apt-get remove --purge guarddog -=- replace the "install" for remove, and if you want the uninstall to remove its files that it created, use the "--purge" option...

Cases when you would use the "purge", and when you wouldn't:
use purge when you want to completely remove the stated program...
don't use purge if you intend to turn right around and re-install - this would keep your config files unchanged, so that after you re-install, the configs would be remaining...

Hope this helps,
Ms. Cuddles