We started using VS 2010 and were very happy with it, so we converted our project into a 2010 solution (still .net 3.5) and continued our development in 2010. However, we ar
Assuming that your solution is under source control and the migration from VS 2008 to VS 2010 was the only change in that checkin, just compare the two version and see what's changed.
Then change the lines affected back to the VS 2008 version and you should be good to go.
There's no automatic process as Microsoft see this as a one way operation.