This Worked for me. Hopefully it will work for you people also.
Initially, I had tried these many things :
Open command window and navigate to C:\windows\microsoft.net\framework \v1.1.4322 Type in aspnet_regiis -u Once finished uninstalling ASP.NET type in aspnet_regiis -i (It was working sometimes but not always).
I tried by Clearing the vswebcache of Visual studio 2003, as per some forum answer, but didn't work out.
Then finally, I used my own technique and it worked for me. I took the old dll's for the project which was not getting load and i had replaced the dll's with old project dll's. After that my project got load into visual studio 2003. There will be one dll and pnb file with name of project which will get corrupted sometime and your project wont get load into IDE.
So, if you face similar issue, then you have two options:
1) Replace the Dll's with old dll's.
2) Delete the Dll and pnb file with project name and try to reload it again.(Deleting the dll is not going to affect your code and other dll's).
Hopefully it will work for you too :)