Hiya fellow Aussie
You shouldn't need to do anything out of the ordinary to install Crysis on Win7. Installs just fine (via Steam & DVD) on my x64 Pro install.
Patches are available from the Downloads link: http://www.gamesas.com/download
You want Wars 1.5, Warhead 1.1 and Crysis 1.2 (1.21 if you want to play online)
Cheers!