Windows 95, 98, and ME do not require unique serial keys. This was the good old days when software did not "phone home" and tattle on you.
In fact, 95, 98 and ME do not technically require serial keys at all. It is just a formality.
On Windows 95 it is extra easy. You may override the install type (no serial needed) by creating a file name MSBATCH.INF with the lines "[Setup]", and then "ProductType=1", placing that in the Win95 setup folder, and then running setup. (on 98 and ME this requires an extra binary edit to one of the setup files but is not too hard).
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In fact, 95, 98 and ME do not technically require serial keys at all. It is just a formality.
On Windows 95 it is extra easy. You may override the install type (no serial needed) by creating a file name MSBATCH.INF with the lines "[Setup]", and then "ProductType=1", placing that in the Win95 setup folder, and then running setup. (on 98 and ME this requires an extra binary edit to one of the setup files but is not too hard).