To push a registry hack via SMS to Win 9x clients you can create a SMS Package containing a batch file with the following code:
regedit /S \\FILEServer\Install\batch\filename.reg
In the same directory as the .reg file add a file named yes.txt. Open yes.txt and add the letter "y", save it, and close it.
echo off , cls will cause any batch file to run silently on Win 9x PCs