Based on service manuals and user reports:
Sony did not release Windows 10 drivers for this model. Windows 7 is the last officially supported OS. Attempting Windows 10 will result in missing drivers for SATA, Power Management, and Sony-specific utilities. Sony Vaio Pcg-31311m Drivers Windows 7
Without these, Windows 7 will run, but:
Because Sony has restructured its support websites and Vaio has changed hands, finding the correct Windows 7 drivers for this specific model can be a maze. This write-up outlines the correct driver packages, installation order, and troubleshooting tips. Based on service manuals and user reports: Sony
If the above seems overwhelming, several preservation communities have created for the PCG-31311M. The most reliable is from VaioDrivers.com (clean, but double-check with an antivirus). Alternatively, the DriverPack Solution 17 offline version (choose “Expert Mode” – never “Auto Install”) can detect and install all drivers, including the Sony utilities. Without these, Windows 7 will run, but: Because