Older Sketchup

How can i download older pc versions of sketchup?   I have some older drawings that I need to open without converting them to the new version...

Also, I do not want Sketchup Pro, I just want to use the original PC version of sketch-up make not the online version.  How can I get this?  I am not going to use the web version for several reasons.  First, the issue of who owns the intellectual property of any design, because like google, once its on Trimble's server it is considered Trimble's property.  Second, the amount of bandwidth required to continually display a 3D image is way higher than most internet connections.  Third, I wouldn't pay for sketchup pro when there are actual  professional cad programs available for equal or less than sketchup.