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Some really old printers are not compatible with Windows 10. What is the model number of your printer ?
That printer is very old and there are no official software and driver released by Lexmark for Windows 10. So it is not official supported. However, you may be able to setup it using older Windows driver. This might not work, but it is worth a try. There are two methods you can try to add it to your computer (if it is supported)
Method 1 :
Download the Windows 7 driver from here --> http://support.lexmark.com/index?page=product&segment=SUPPORT&productCode=LEXMARK_X2500&locale=en&userlocale=EN#2
Open the downloaded printer file and follow the onscreen instructions to setup it. You can also the disc came with the printer to setup it.
Method 2 :
Press Windows and R keys and this will bring Run. Type control printers and press enter. Click Add Printer and see if it can be recognized by your computer. Let me know how it goes