The best practice to remove the .svn files/folder from a svn repository is the request of an export to the svn system.
It is really simple, from the command line you can issue a command like the followng:
The above command will export a clean directory tree.
Sometimes happens that you are not able to connect to the svn server and you have a working copy on your PC. To remove the svn files/folders you can write a simple batch script like the following:
and then, you have to run it from the root directory of your working copy.