|Some computers are slow when they come out of hibernation, depending on what settings you have in place for devices shutting down or simply using minimal resources...|
Does the performance of your PC normally deteriorate if it's been on for a while? It could be an overheating issue. I'd take a look at the temperature of the CPU to keep an eye on that.
You say that Windows mentioned a file not found. Do you remember what file it was referring to?