RVHOST.EXE is missing error

This means that RVHost has been infected or is a virus that has been detected already by your anti virus and removed. So to remove the Error message follow you have to edit your registry, just this steps:

Start>Run>Type regedit then

Look for  this:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

then on right pane look for "Shell"

Its entry should be "Explorer.exe" only
If it’s has extra like “RVHOST.exe” remove it.
Double click the “Shell” then edit.
Then close and restart your PC.
And your Done!!