Can't activate avast

I recently had to reinstall my windows (vista business) and since I cannot activate avast. Downloading went fine but it didn’t wanted to work out. It says theres something wrong with RPC. Whats that? It also says Unknown problem, standard shield provider not found.

RPC stands voor Remote Procedure Call

http://en.wikipedia.org/wiki/Remote_procedure_call

sounds like your RPC service is not running on your computer…
check in the SERVICES screen if its running, if its not start it and try again

remove the file and download again. seems like install file is corrupted during the download
http://smileyhost.net/9/e/i.jpg