If you have "Vista Internet Security 2010" specifically (there's various rogue AVs out there, simply varying in name), you can do this.
1. In task manager (ctrl-alt-del), kill this process.
av.exe
2. In regedit, delete these registry values.
HKEY_CURRENT_USER\Software\Classes\.exe\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "%1" %*
HKEY_CURRENT_USER\Software\Classes\secfile\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "%1" %*
HKEY_CLASSES_ROOT\.exe\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "%1" %*
HKEY_CLASSES_ROOT\secfile\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "%1" %*
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\FIREFOX.EXE\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "C:\Program Files\Mozilla Firefox\firefox.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\FIREFOX.EXE\shell\safemode\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\IEXPLORE.EXE\shell\open\command "(Default)" = "%UserProfile%\Local Settings\Application Data\av.exe" /START "C:\Program Files\Internet Explorer\iexplore.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center "AntiVirusOverride" = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center "FirewallOverride" = "1"
3. Delete the files.
%UserProfile%\\AppData\\Local\\av.exe
%UserProfile%\\AppData\\Local\\WRblt8464P
search for av.exe and delete any more
4. Get a virusscan and scan your computer.