That heapen when your source was make it with a newest version not VS 2K3 maybe if you wanna build correctly use 2010
When it's build with VS 2k10, then I would go for VS 2k12 since it's fully compatible with VS 2k10 sln files.
You can check the file format when opening the sln file with your notepad. v11 and v12 is fine with VS 2k12. When it has v11 you can go for VS 2k10, too.