unfortunately removing unpleasant programs is not always simple as the author maynot want them removed!
I agree with gerbil there are programs and searching google may well find others to do the trick of removal
Another more dangerous way if you do not know what you are doing is to use regedit, go into the registry and (have done a backup of registry see file menu) delete any key that has a reference to Virtumonde (or any associated texts etc that appear unwanted on the screen) You may have to delete asszociate'd files as well.
This method has to work as in the last resort it is the registry that controls the operations.
If all goes well close down fully and normally and restart.
if it all goes belly up then restart in safe mode and go to regedit and restore the backed up copy of the registry that you made.