After update i lost my project, how can i get it back?

I installed unity 4 over my previous unity 3.5, the project i was working on is now gone when i launch unity, how can i get it back? where do projects save to by default? or have i lost it for good?

It’s wherever you chose to save it, probably in your home directory. Do a search on your hard drive if you have to, and back it up before opening it in Unity 4.