Hi Nick ! Welcome to the forums !
Firstly , you need to get a complete system image backup before you attempt to modify your system files.
When changing explorerframe.dll, first rename the original to explorerframeORIGINAL.dll or something like that, dont delete it. Now put the modified (downloaded, I think?) file in the location , restart (computer or explorer) to see the changes.
Why are you changing the explorer.exe? If it is to change the start button only, better you use Win 7 Start Button Changer 2.0 by ~Kishan-Bagaria on deviantART
. It will change the start buttons without any hazards .
While modifying imageres.dll, save the output of resource hacker on desktop, named imageres.dll . Now rename the original as imageresORIGINAL.dll, and put the modified in location. Restart to see changes. BTW, you need not to do anything with syswow64.
And finally , dont forget to get a complete system image backup before anything .