UPDATE: 16th December: I felt it fair to update the post with my findings
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At my company we have a great DSL based tool for generating WCF Services.
However, because of various reasons, the tool will only run under Visual Studio 2005 and not the all new and great Visual Studio 2008.
That is a pity, because I wanted to show off a new concept and hence wanted to use the WPF designer in 2008 to make an impression for the client.
Well, I’m I thought I was in luck! Apparently I can use the same projects in VS 2005 in VS 2008 and vice versa.
So you don’t have to abandon VS 2005 to try out the new features in VS 2008 in your projects… this is good stuff Microsoft!
I should have read the article more closely: I opened up my VS 2005 C# library project in VS 2008.. and it gave me an upgrade wizard 😦
Luckially I was able to use my assemblies from VS 2008 with no trouble, but it could have been so much better.
Salesforce & MuleSoft Blog 
I’ve just completed a utility that will allow you to convert between VS2005 and VS2008 projects. (It just edits the solution and project files… no other conversion is done).
I’d consider it an “advanced beta”, but folks are welcome to take a look at the VB2008 source code.
http://home.hot.rr.com/graye/Temp/ProjectConverter.zip
Good work! Have you considered hosting this on Codeplex?
Still, what I am REALLY wanting is a way to choose which version of Visual Studio I open my projects with.
When a new version of Visual Studio comes out, then I might want to work on some aspects with the new tools in VS 2008, whilst maintaining other aspects in ‘legacy’ tools in VS 2005.
The ProjectConverter is now complete http://home.hot.rr.com/graye/Articles/ProjectConverter.htm
sir tell me that i am using in home vs 2008 and in my institute i am using 2005 how to convert it..
I would install Visual Studio 2005 on your machine. It can can run side-by-side with Visual Studio 2008.
You ‘could’ work out a method to achieve what you want, but I believe it would be better for you to use one tool (Visual Studio 2005) for your institute projects.