Search into Windows registry with grep/cygwin

I'm trying to search and remove unrelevantregistry keys, and it sounds like Cygwin does allow access to them through /proc/registry.

However, recursive grep -r outputs error lines like :

grep: /proc/registry/HKEY_CLASSES_ROOT/.aspx/@: Is a directory

Strange error for a recursive grep. Then, file displays :

$ file /proc/registry/HKEY_CLASSES_ROOT/.aspx/@
/proc/registry/HKEY_CLASSES_ROOT/.aspx/@: ASCII text, with no line terminators

So it's a file now. I used cat.

$ cat /proc/registry/HKEY_CLASSES_ROOT/.aspx/@
VisualStudio.aspx.10.0

And I can't cd into it, moreover ls -l doesn't display the d flags. Why grep still considers it as being a directory ?

- - , .