There is no real way for the virus to do anything because people never, ever share already installed *.exe files. at least no person in there right mind would do it. Viruses will probably never be big for pocket PCs for two reasons. The first one is that they are not constantly connect to each other and the Internet like desktop PCs. The second reason is that the only thing a virus could do would be destroy information stored in the ram, If a virus deleted or corrupted that info, you could just hard-reset your device and, sync to get all the data back.