Install file won't open?

Well, I'm trying to install a program called process blocker so I can block some really annoying viral processes from starting up but when I tried to start the install file, It would say: " This installation package could not be opened. Contact the application vendor to verify that this is a valid Windows install package." I have windows XP SP3 and I just freshly formatted my hard drive so their should be no interface from other programs. D: help!