You mean the different (and now, nearly annually changed) file versions? Wikipedia has a listing of them under DWG, IIRC.
There is a organization now called ODA(opendwg.org) that is working on an open source version of the DWG format (which I'm sure Adesk is thrilled about).
Inventor Series 2010 SR SP4
Windows 7 64 bit - SP1
8 GB Ram