Why Visual Studio 2005 ask me to convert a solution already got converted

Somebody did the conversion of a solution from .net 1.1 to .net 2.0 by using the automatic conversion wizard of Visual Studio 2005. Then, he changed to another company.
Now, I take over his job. Unfortunately, when I attempted to open that solution, Visual Studio 2005 prompted me the conversion wizard again to forced me to perform a conversion on the solution. Does someone know why?

Thanks