I installed VS2008 SP1, then I needed VS2005 SP2 (since I needed to open BIDS2005 projects without thier conversion to 2008).

I needed to .NET 1.1 compatibility and installed VS2003 + SP1.

Npw all my VS2005 and VS2008 projects (solutions) are being associated with VS2003. I.e. double-clicking opens VS2003, telling that it does not recognize them!

How can I restore correct associatons of  the proj and soltions (.csproj, .sln) files without reinstalling VS2005, VS2008 and all their service packs?

Run devenv /setup from Visual Studio 2005 and 2008 command line prompt

http://msdn.microsoft.com/en-us/library/ex6a2fad(VS.80).aspx

Nowall, thanks,
it is curious that
devenv /?
does not output this option as available.

This command takes so much time to run that
I suspect it is the same as running setup, only without GUI.

With GUI or without,
my question really   implied another question:
Should I run also the  service packss after reinstall of VS2005 and VS2008?
are there any shortcuts bypassing all these?

And how can I determine such necessity?

Now, I ran
devenv /setup
both for  VS2008(first) and, then, VS2005 (using their cmmand lines).
After that,  I still have VS2003 launched on double-clicking VS2008 .sln files.

BTW, the mentioned link tells:
"Forces Visual Studio to merge the resource metadata that describes menus, toolbars, and command groups from all VSPackages available."

It does not mention anything about Windows associations (from outside of VS)

guenavan:

I ran
devenv /setup
both for  VS2008(first) and, then, VS2005 (using their cmmand lines).
After that,  I still have VS2003 launched on double-clicking VS2008 .sln files.

 
I regret that I ran
devenv /setup

I just worsened the situation

Now, trying to launch VS2003 webapp proj I am getting

---------------------------
Microsoft Development Environment
---------------------------
Visual Studio .NET has detected that the specified Web server is not running ASP.NET version 1.1. You will be unable to run ASP.NET Web applications or services.
---------------------------
ОК   Справка  
---------------------------

And
Inetmgr.exe --> websites --> Properties ---> ASP.NET --->
ASP.NET version:
combobox has only one choice
2.0.50727

Considering the problems of developing 1.1 in parallel with 2.0, I suggest that you install VS2003 in a virtual machine and VS2008 on the host machine (or in yet another virtual machine).