DLL's (dynamic link libraries)usually live in the windows/system folder. If you ever have to put one there PLEASE read any warning that appears such as "do you wish to overwrite....". If you are at all unsure, take the do nothing exit. If you want to try a different version of a DLL, firstly re-name the old one by changing the file type extension from .DLL to .DLLOLD. Copy the new one to the folder (no warning this time) and try it. If it all goes pear shaped, delete the one you added and re-name the .DLLOLD to .DLL and you are back where you started.