select CUSTOM install
ignore all fields EXCEPT the machine ID field, put 2 for machine ID
let it install.
Go to start > run > services.msc
you should now see 2 FAH services, fah and fah2
right click FAH 2 and choose STOP
go to your first instance and copy the config file
go to your second instance folder that you just installed
paste the config file there
open config file and only change the machine ID from 1 to 2
go to start > run > regedit
hkey local machine > system > current control set > services > FAH2 > AppParameters
paste this in the key: -service -advmethods -forceasm
go back to services and start the service.
Happy 2 instance folding!