Vista Internet Security and other fake antivirus with the same behavior will give you the following notification and/or pop up messages.

To remove some pop ups, go to task manager (CTRL+ALT+DELETE) then go to
Processes tab. Look for
av.exe and left-click on it. Click on
end process. Click OK to terminate the process.
The following steps are also applicable to related fake AV (
XP Antivirus/AntiMalware/Guardian/Internet Security 2010 and its
Vista counterpart) having av.exe or ave.exe as the executable file.
To check the exact location of the av.exe:
- Click START button and on the search box type regedit
- On the Registry Editor window, press CTRL+F to use the Search function
- Find av.exe
Usually found under this directory:
HKEY_CURRENT_USER\Software\Classes\.exe\shell\open\command
HKEY_CURRENT_USER\Software\Classes\secfile\shell\open\command

Right-click on
Default and click
Modify to see the exact location


Go to that location to manually delete av.exe. You must show the hidden files first to find it easily:
- Go to
Control Panel- Switch to Classic View and double click on
Folder Options- Click
View tab
- Select "Show Hidden Files and Folders" and uncheck "Hide extensions for known file types" and "Hide protected operating system files"
- Click
Apply then click
OK
Furthermore, you have to add/remove permission on the file you have to delete. Just set it to Allow or simply click on Clear All on the file properties window.

And here's the irreversible effect after deleting av.exe:

The "Open With" prompt can be resolved through the use of file association fixes:
OpenWithPatch.
Here are the related articles to fix the "Open With" issue:For Windows XP: Download
exe file association fixFor Windows Vista and Windows 7Note: If you are not able to download those files, create the registry fix manually.
- Open Notepad and copy and paste the following
Windows Registry Editor Version 5.00
[-HKEY_CURRENT_USER\Software\Classes\.exe\shell\open\command]
[-HKEY_CURRENT_USER\Software\Classes\secfile\shell\open\command]
[-HKEY_CLASSES_ROOT\.exe\shell\open\command]
[HKEY_CLASSES_ROOT\.exe]
@="exefile"
"Content Type"="application/x-msdownload"
[-HKEY_CLASSES_ROOT\secfile]
Save as
exefix.reg on your Desktop and file type should be
All files.