My computer got infected by a virus, this changed the administrator rightshence cannot install the antivirus...what can I do?

Hi Please understand that the officially recommended method is to format and re-install the compromised computer from a known good build (i.e. operating system CD + all security patches while disconnected from the network), because it will be more stable after format and re-install the system, and it is hard to guarantee that the system can be fully recovered after it has been infected. For more information on hacking, please refer to these links: Help: I Got Hacked. Now What Do I Do? http://www.microsoft.com/technet/community/columns/secmgmt/sm0504.mspx Help: I Got Hacked. Now What Do I Do? Part II http://www.microsoft.com/technet/community/columns/secmgmt/sm0704.mspx How A Criminal Might Infiltrate Your Network http://www.microsoft.com/technet/technetmag/issues/2005/01/AnatomyofaHack/default.aspx Malicious Software Removal Tool http://www.microsoft.com/security/malwareremove/default.mspx The Day After: Your First Response To A Security Breach http://www.microsoft.com/technet/technetmag/issues/2005/01/IncidentResponse Get a free safety scan for your computer http://www.microsoft.com/protect/products/computer/safetyscanner.mspx The WindowsVista Security Software Providers website includes all anti-virus products which are compatible with Vista. Some of the partner sites offer free online scanners which will search your computer for the latest viruses. If you need more help on virus-related issues, you can also contact Microsoft Product Support Services. For support within the United States and Canada, call toll-free (866) PCSAFETY (727-2338). For support outside the United States and Canada, visit the Product Support Services Web page (http://support.microsoft.com/?pr=SecurityHome). Hope it helps. Thank you for your time and cooperation. Sincerely, Joson Zhou Microsoft Online Community Support