aswmonVd.dll An installable virtual device driver failed dll initialization.Uninstalled avast and ran avclear and rebooted error still occurs.Reinstalling avast didnt help. ???
Maybe (maybe) your problem is with one registry value (suspect this if you had Norton on that machine).
See here: http://www.avast.com/forum/index.php?board=1;action=display;threadid=259;start=0
If you have Norton Antivirus, forget avast.
I recomend the oposite: forget NAV, come to avast ;D
Desinstall Norton, use RNAV2003.exe (from Symantec), try a good Registry Cleaner (see http://www.avast.com/forum/index.php?board=1;action=display;threadid=834 or download http://www.vtoy.fi/jv16/programs/jv16pt.zip - jv16 PowerTools 1.3.0.196.zip) and pray man! 
Never had norton on the system jv16 wasn’t able to delete registry entries and the registry entries are definitely related to avast not norton.
Check out \windows\system32\config.nt and remove all references to avast (should be at least one in there). That should fix the prob.
Vlk
looked in config.nt no reference to avast but error keeps referring to dll initialization error any further ideas ???
In this case look in the registry
(unless you have WinXp use RegEdt32.exe instead of RegEdit.exe as it is able to cope with multi-string values):
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\VirtualDeviceDrivers
value called VDD. Remove the reference to aswMonVd.dll from there.
Vlk
removed the aswMonVd.dll file in registry virtual device drivers all my dos based programs stopped working. Reinstalled avast and everything ran great. ;D Thanks to Vlk,technical and kubecj.Really appreciated.
done all the above but still not working
I have uninstalled Avast! after multiple uninstalls/Reinstalls, but it still doesn’t work 
I’ve emptied VDD, and restored the original autoexec/config/command files but it doesn’t have any effect… Anybody know what I can do?
You must have the following entry there:
C:\Program Files\Alwil Software\Avast4\aswMonVd.dll
Check all these keys (if you have them all):
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\VirtualDeviceDrivers\VDD
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\VirtualDeviceDrivers\VDD
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\VirtualDeviceDrivers\VDD
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Control\VirtualDeviceDrivers\VDD
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet004\Control\VirtualDeviceDrivers\VDD
As I wrote, I have now uninstalled Avast! Antivirus, and the default file on the windows CD does not contain that line. Therefore I’ve emptied it…
So, you’re not scanning the 16bits applications (DOS). You need that key for proper working of avast.
Try running pkzip.exe (for DOS) for instance…
Did you have the ‘default’ file on config.nt or the edited one?
I have removed the whole Avast anti virus software, not just the registry file…