antivirus system pro

I cannot remove antivirus system pro.
It will not let me download the malwarebytes.
When I download it from another comuter and put it on the effected one it call for a registration number and to get that it says that I must purchase the program. Am I doing something wrong?

• Download combofix from here
  Link 1
  Link 2
  

1. If you are using Firefox, make sure that your download settings are as follows:

* Tools->Options->Main tab
* Set to "Always ask me where to Save the files".

2. During the download, rename Combofix to Combo-Fix as follows:





3. It is important you rename Combofix during the download, but not after.
4. Please do not rename Combofix to other names, but only to the one indicated.
5. Close any open browsers.
6. We need to disable your local AV (Anti-virus) before running Combofix.

• See HERE for how to disable your AV.
  
• Double click on ComboFix.exe.
  
• Follow the prompts. NOTE:
  
• ComboFix will check to see if the Microsoft Windows Recovery Console is installed.
  ***It's strongly recommended to have the Recovery Console installed before doing any malware removal.***
  
• Allow combofix to run
  
• Post C:\combofix.txt back here.
  
  Note:
  Do not mouseclick combofix's window whilst it's running. That may cause it to stall.