In order to delete all \".svn\" files/folders/subfolders in \"myfolder\" I use this simple line in a batch file:
FOR /R myfolder %%X IN (.svn) DO (RD /S /Q \"%%X
you can try
FOR /R myfolder %%X IN (.svn) DO (RD /S /Q "%%X" 2>nul)
Something like that using find :
rm -rf `find . -name ".svn" -type d`
Edit:
I know this is for linux (I read bash instead of batch). I'm leaving it here to help Linux users that would randomly end-up here :)