The .reg file type is normally used to modify the registry and it may be that your registry editor is detecting that it isn’t a proper .reg file.

When you say “I have used RUN %temp% and tried to delete the file from there but everytime i reboot my machine the same error message appears: WARNING A VIRUS WAS FOUND!”
Do you mean it can’t be deleted, if so what error is displayed ?
Or do you mean it comes back to the same location ?

Did you run the avast boot-time scan as suggested and if so did avast detect 1.reg and give you options ?