Create a blank svnresistry.reg file (can be any name with .reg extension) on your desktop, edit it, and copy the following code snippet as its content.
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Folder\shell\DeleteSVN] @="Delete SVN Folders" [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Folder\shell\DeleteSVN\command] @="cmd.exe /c \"TITLE Removing SVN Folders in %1 && COLOR 9A && FOR /r \"%1\" %%f IN (.svn) DO RD /s /q \"%%f\" \""
Double click the reg file to execute it.
Then you can right click on the project folder, you will see a 'Delete SVN Folders' menu.
Just clicking on this menu will remove all the 'svn' folders under this directory recursively.