Duplication of Firewall on second PC

I use Personal Firewall latest update on this PC [XP] but I have a second backup [XP] PC - both are desktops running alternately from the same internet connection - where the security is out of date by several months due to non-use. It may be that the Comodo Firewall on that PC is sufficient but I would like to update it.

Is it safer to download some current installation or update file onto a flash drive and from there transfer it to the second PC [rather than do the download directly online and risk a breach of security?].
Are there proper steps and a procedure for doing this?

What version are you trying to update?