Try this script...if competitve uninstall did not work...

1. open a notepad
2. type msiexec /x {Product code of CA Etrust 8.1} /passive or /quiet
    /passive - visible uninstallation     /quiet - silent uninstallation
3. Save this notepad as a .bat file
4. Run this .bat file on the machine which has CA etrust 8.1

Product code can be obtained from the registry

HKLM \ Software \ Microsoft \ Windows \Current Version \ uninstall.

Under the unistall folder you would find multiple folders respective to each application. Find the right folder for CA etrust 8.1 and copy the product code from Dword string Uninstall String or Modify Path