Inventor 5.0 is 10 years old. It is a 3D modeling software package to help envision how parts will look, fit, be shaped and assembled. It is not a drafting package. AutoCad is notoriously bad about not offering a list price on any of their products. A guess would put the 2010/2011 stand-alone Inventor at least $1,500.
Inventor 5.0 is not a prototype package like the later versions, just a high quality 'visualizer'. Even so, it's not a piece of meat either. Float it on eBay at some number that makes it worth your trouble -- $100? $250? $300? If it doesn't sell see if a school or training center would like a donation. If not, then the disks would make some fine skeet shooting.