Is it possible to open 2010 files in 2008 or can 2010 back save the files so that it is possible for 2008 to open them?
I don't think so.
It is not possible unless you play games and save the 2010 file in a different format (step, stl, etc) and try opening that in 2008. This will likely result in a "dumb-solid" with no editable features. If you have SWorks Pro or premium you could run it thru FeatureWorks and see if it recreates any features. It will be less than perfect.
Why are you trying to save 2010 files in 2008 format?
My supplier has not yet upgraded from 2008.
then you should save as .x_t files for them, which are parasolid. This is the native kernel for solidworks, so the files shouldn't have any translation issues. Then they can use your models as reference. They will not have any design history with them (no tree, just a dumb solid).
When they complain, you can politely request that they upgrade.
If your supplier just want to view the files, you can send him 3D PDF or e-drawings (he can install e-drawing viewer 2010)
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