Even Xerox support & drivers returns “No results for phaser6125”.
Believe me, I have searched for years. Many support forums of all kinds have phaser6125 owners trying to find drivers. The phaser6125 was apparently an el-cheapo special production with no support beyond Win7.
something I have found. Manufacturers use the saem driver though several different models. In fact Linux “Generic” Drivers drive just about everything. I will bet that the link I gave you for the 6200 series “Package” will also drive the 6100 series.
And again... If you can’t even find Windows drivers for it then it is an obsolete dinosaur and ready for the trash bin. Time for a new one so that you can move on and update.