My answer would be: Install and run Trend Micro’s System Information Collector (SIC). While this will not remove the malware, it will help you define what needs to be removed. Then review the Vundo article and determine what measures are applicable.
I notice that this has been tagged with “Virus prevention”. This is not a prevention issue. The damage has been done. This is now a recovery and repair issue. The recommendation that should be given is “restore the machine to a saved trustworthy state”. Removal tools, such as Malwarebytes Anti-Malware (MAM) are incomplete measures. They cannot restore deleted files, they cannot identify malicious configuration changes. There are many measures these repair programs cannot take. They will stop popups. I doubt there is a restore point you can return to, but perhaps others can learn from this experience and learn about saving their system state in case they find themselves in a similar situation.
Sometimes, antivirus software also create virus program they convert itself to a virus or some form of malware. You have mentioned that your computer is running in Windows XP and it is really an OS which is vulnerable to viruses. The best thing you have to do is to first back up your important files, and reformat your computer. After that, install a Windows Vista or Windows 7 Operating System since it is more reliable when it comes to virus protection.