You need to specify your PC specs. It could be that the PSU is inefficient for a recent hardware replacement (like a better video card).
Usually, when your PC is put to sleep (sleep mode or hibernation) the last session is held in virtual space and any disruption can actually damage the hard drive as well as the operating system.
Sleep mode or hibernation is really for laptops but can be used for desktops but is only as a standby mode if you are away from the Pc for more than 20 minutes or less than 5 hours. Using those modes for more than 6 hours or overnight or days (!) can have detrimental effects especially if the last sesion included many programs already opened like Office, web browser, music player or a movie. All that data is held in temporary storage allowing the user to wake it and continue without having to open each app again however, that pressure of the hdd can cause a complete disk failuire if too many apps were opened prior to sleep or if there was a power outage in which case, the session would have been lost and severe fragmentation or hdd damge would have occurred.
What was the output power of the old PSu and what output wattage of the new PSU?