HP says this driver is compatible with windows 7.

https://hp-laserjet-m1120n-multifunction-printer-drivers.en.softonic.com/

Install the latest driver for m1120n mfp

Download the latest and official version of drivers for HP LaserJet M1120n Multifunction Printer. This driver package is available for 32 and 64 bit PCs. It is compatible with the following operating Systems: Windows 10 (32-bit), Windows 10 (64-bit), Windows 8.1 (32-bit), Windows 8.1 (64-bit), Windows 8 (32-bit), Windows 8 (64-bit), Windows 7 (32-bit), Windows 7 (64-bit), Windows Vista (32-bit), Windows Vista (64-bit), Windows XP (32-bit), Windows XP (64-bit), Windows 200, Windows Server 2003. Don't worry if you don't know what's your operating system. HP website will automatically detect your device and select the best installer for your OS.