Latest versions of the Adobe suite are all CS2 (CS stands for Creative Suite).
Illustrator CS2 is basically Illustrator 12.0
Photoshop CS2 is about Photoshop 9.0
InDesign CS2 is InDesign 4.0 I think...
The latest (CS2) versions are big. I have 2 gig of RAM and things still slow down dramatically when dealing with big Photoshop and Illustrator files. So make sure your PC can handle them.
With regards to Illustrator, the latest versions add mainly Live Tracing, Live Painting and 3D effects, so if you don't need that functionality then you could be able to get away with using Illustrator 10 or CS1 if you find them cheaply. Avoid Illustrator 9.0 like the plague.
I know nothing about Macs, however...
PS Oh yeah, if you're buying software online make sure you do so from an Australian software vendor as international legal and marketing crapulence prevents sale of digital stuff online from the US. I may be wrong, but I know you can't buy computer programs from Amazon and ship to an Australian address.