Blender Wont load into Unity

I keep trying to import a model that I created in Unity but every time I try Unity says

[Blender could not convert the .blend file to FBX file.
You need to use Blender 2.45-2.49 or 2.58 and later versions for direct Blender import to work.}

I have blender 2.71 for Windows Vista…whats happening!

Never import blender (or 3dsmax or maya) files into Unity. Unity doesn’t support those file formats. It just tries to convert them into FBX if you have the correct application installed (blender or maya or 3dsmax). If you share your project with a different developer, he won’t be able to run the project without having blender (or others) installed.

Always export your models into FBX file and only import FBX files to Unity.