This looks like
it is going to be hard work!
I saw from the web site's FAQ that you need to uninstall this through their own server, but I have also seen reports that it does not work, and one report that asks if the web site is out of business. That makes removal more difficult.
Start an elimination process;
1] Check XP's Services Console, (Start > Run, type in services.msc and click OK). Look for anything that suggests it belongs to this. If you find anything, disable the service.
2] Open the Task Manager, (right click the Taskbar, select Task Manager), then the Processes tab, and look down the list for anything that might be associated. You may need to check processes in Google.
3] Try a utility called Process Explorer to drill down deep into what the processes are using, and track to where this app has left traces.
4] Open the Registry Editor, (Start > Run, type in regedit and click OK), and drill down to the "Run" Keys, and delete any key/value relating to this app. The keys you need to check are;
Keys 1-4 are run each time a new user logs in.
Keys 5-6 are run in the background when the logon dialog box first appears,or at this stage of the boot process if there is no logon. These keys are for background services such as remote registry service and are run only once per boot.
Key 7 is run as part of Setup's first-boot activities, or after you use the Add/Remove Programs Wizard.
BEWARE - I won't be held responsible for any changes you may make to the registry which causes more problems. Changing the registry is at your own risk and incorrect changes can kill the OS dead. Make sure you understand how to use the registry, and how to recover from any corruption. The link below may help.