The only DX related file that you have to worry about is the
d3dx9-soething-or-other.dll file that's in your EQ folder. That's an EQ specific file that is maintained by SOE/Verant. An easy way to make sure you have all the files you need for a backup would be to drop to the command line, go to your EQ folder and do the following:
Code:
mkdir EMu_backup
copy *.exe EMu_backup
copy *.dll EMu_backup
copy *.ini EMu_backup
copy eqhost.txt EMu_backup
All you have to do is, after you patch (if you're still able to play on EQEMu servers), just re-run those commands to back it up again.
If you happen to patch and it breaks EQEMu, then just copy the files in your EQEMu_backup folder back into your EQ folder.