I am not sure I have the capabilities to provide "working drivers" as it sounds more like you are having a problem with missing files in the registry if you cannot install the printer with the plug and play drivers.
Try the HP Printer Install Wizard and hopefully that will get you printing again. I recommend trying the suggestion in this link to totally solve your problem though:
--There's No Driver For My Printer--
I could not find the product specifications for the PSC 750 to determine which printer language it uses but you may be able to install the Deskjet 990c driver or the PSC 750xi instead.
Let me know if this helps you.