You should purchase the EMS client, it is excellent! The Vulnerability Management and web filtering is easily worth the price. The AV is very good and hasn't had a false positive in some time. (Can't say that about MBAM!)
Don't forget you probably get 10 free with your firewall. Try it out. Then buy it, it's great.
However, if you want to use the free AV client from FortiClient.com, you can follow this procedure:
- with a computer on the internet, browse to FortiClient.com and start the download
- open the temp folder by clicking start-> run and choosing %temp% as the value
- look for new folders and files to be created, this is what you need
- once the "one time" AV scanner starts, you can close it out. No need to get it, unless you want to do that too.
- proceed into the installation as if you were going to install the client
- look for an MSI file to be there about 75MB
- copy that file out to your desktop
- you can cancel the installation now
- copy that MSI file to a flash drive and go to the machine which needs AV
- temporarily give that machine Internet access (yes, I know) so that it gets current AV defs
- remove that machine's temporary internet access
(although if you could do that... sigh)
From what I can see, this should be allowed since it is only using software already on the public free side.