Did you look here?
Sony eSupport - DSC-S750 - Software Updates & Drivers

Try to Scan for hardware changes in the device manager. your USB must be plugged in when you hit scan for hardware changes.
Sony eSupport - Electronics - Support Information
If you look at this link it will give you the driver for it and all the online/ or call in support you need to fix your problem.
It will be good to try that opinion.If all fails call Sony and ask for tech support.