I have a VS project (made by someone else), and when I try to open it on Visual Studio 2008, I get the following error message:
"The selected file is a solution file, but was created by a newer version of this application and cannot be opened"
I would have thought VS was backwards compatible. Is there any way I can open this?
VS is backwards compatible, yes - you can open a VS 2005 solution file in VS 2008, for example. It's not forward compatible though - presumably that solution has been created by someone with VS 2010. EDIT: According to comments, with VS2010 SP1, you can open VS2012 solutions. I haven't verified this myself.
Fortunately, although the solution files aren't compatible, I believe you should be able to create a new solution in VS 2008 and add the existing project files created with 2010, so long as they haven't used any VS2010-specific features (either in the project structure or in the code itself). If the code targets .NET 4, you may need to adjust the project file to retarget it to .NET 3.5, too.
You may well see a warning about this (an unknown tools version, or something like that) - but it may very well work. I have a number of projects which have separate solution files for VS2008 and VS2010, but which use the same project files.