Alpharom or securom; there are various cracks in other threads of this section and probably one of the will work; same interact with a dll in the modules folder, same with the exe and other else with same logs generated in the user folder or all-users folder; i can't be more specific because there are various version of the protection and various cracks.
Note also that kdays.dll doesn't really exist beside the crack; the usage of kdays.dll is linked to the crack since the game executable or one of his dll is patched to force it to load kdays.dll instead of user.dll (not sure if is this one); kdays.dll is deployed from the crack and replicate a function normally present in user.dll that tell the game about the regionals of windows, so kdays provide fake informations;
since kdays emulate only a few functions doesn't work with same game (missing functions entry point errors xxxxx blah blah blah), and probably will be expanded in future!;
so don't put it in windows folder because may prevent new version of the crack to work because windows load the dll's inside the windows folder first, that may became older than the one deployed from the cracks in the game folder.