I am using Visual Studio 2005. After taking code from version control first, the c#.net application runs correctly. But, after doing some modifications, when I build I am
You aren't supposed to change the folder attribute to not-readonly. The reason you are seeing this error message is that source control assumes that you only store your miscellaneous files somewhere other than bin folder, for it it reserved for files that are automatically created by .Net and it doesn't want to add them to source control.
I suggest instead of using Environment.CurrectDirectory (which I assume you are using currently), you create a folder named "MyProjectName" in %appdata% address and then use:
System.IO.Path.Combine(Environment.GetEnvironmentVariable("appdata"),"YourProjectName").