Not sure why you want to remove Secunia. We recommend folks use it and even provide this topic: How to detect vulnerable and out-dated programs using Secunia Personal Software Inspector
If you're concerned about Secunia running at startup...you can disable that feature and use it when you want. To do that open Secunia and select the settings tab. Then clear the checkmark next to Start the Secunia PSI on boot.
Anyway, the correct way to remove most programs is from within its program group Uninstall shortcut in Start Menu > All Programs or by using Add/Remove Programs
or Programs and Features
in Control Panel.
Alternatively, you can use a third-party utility like Revo Uninstaller Free or Portable
and follow these instructions
for using it. Revo provides a listing of all installed software by installation date and when removing a program, Revo does a more comprehensive job of searching for and removing related registry entries, files and folders.
Keep in mind that not all programs show up in Add/Remove Programs or Programs and Features. Some will have their own uninstaller, which can be found in the program's folder. This is by design as some vendors write installation routines so their program will not be included in the Add/Remove list. If the program is not listed in Add/Remove or Programs and Features, look for an uninstall icon (shortcut) from within its program group. Click on Start > All Programs (or Program Files), look for the program folder by name and use the program's uninstaller.