Not only is the solution conversion wizard unable to convert your 2.x projects, but you can't load them into the Visual Studio at all! Let's see how to overcome it without the need of creating a completely new project.
To make your project at least openable, very simple change in a text file is needed:
If you use solutions, Visual Studio would still try to convert them, although now it will succeed. However, if you want to skip this step, you can "upgrade" your solution files yourself too.
Open the .sln file in Notepad (or your favorite text editor) just like in the previous case. This time, however, you will see plain text starting with these lines:
Microsoft Visual Studio Solution File, Format Version 9.00
# Visual Studio 2005
Just change it to:
Microsoft Visual Studio Solution File, Format Version 10.00
# Visual Studio 2008
(remove any empty lines at the beginning) and save the file.
Now it should have the icon with digit 9 in a box, and you should be able to open it as usual, without any wizards.
Despite the fact that the manual upgrade steps are quite easy to do, it still requires your time, especially if you have several projects to convert. So here is a little tool (ZIP, 35 kB), on which you can drag any solution or project files and it will automatically do conversions for all projects in the solution(s) using the steps above.
Moreover, the tool scans all the project files and tries to do these updates:
Modified files are being backuped. Enjoy!