I downloaded AVAST 4 Home Edition 4.0.172
When I try to run it i get an error message that ASWCMNB.dll cannot be found. What do I do? >:(
That file is located on my computer at C:\Program Files\Alwil Software\Avast4 .
Maybe your download is corrupted. The downloaded file should be 6.25MB (6,561,968 bytes).
If the size of the file you downloaded is different, try redownloading it.
aswCmnB.dll is a vital part of avast. It is one of its root libraries. Without it, there is really no chance avast will run. 
It’s probably a badly damaged installation - I recommend downloading and installing the program again…
Vlk