After installing Mr. Driller, when attempting to open the program, you will be asked for a product key. The following key will allow you to play the game:
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                    ALC3-E4NW-2CY3-2WLE
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Each time opening the program, you will be asked for a key, even after having entered it once. However, this can be fixed by performing the following:
1) Navigate to the folder you installed Mr. Driller to. The default path is Program Files (x86) --> namco --> driller on 64-bit Windows 10.
2) Open driller.ini in Notepad, and find the line with REGIST1=. You will want to replace this line with the following:
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                  REGIST1=ALC3E4NW2CY32WLE
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After this is done, save the file. You may have to save it outside the install folder and copy it to the folder manually.
3) Open the program, and you should be brought past the product key prompt to the game's configuration panel.

Happy drilling!