Question:

Is it OK to put the computer on "hibernate" each night or is it best
to shut it down completely?

With all the virus, etc going on what is the best way to go?

Answer:

The best thing to do, is to shut down the computer.

When you turn your computer on, it loads Windows from the hard drive (which is long-term, stable storage) into RAM, (which is short-term, more volatile storage) where it stays until you shut your computer down.

When you put your computer into hibernate, the computer copies the contents in the RAM to a spot on your hard drive and goes into a power saving mode. When you wake the computer back up, it copies the contents of that file back into RAM and picks up where it left off. If there were any errors that had occurred with your data, the errors would be copied as well.

When you shut your computer down at the end of the day, it saves your files, and any configuration changes you may have made (like a change in wallpaper, etc.) and shuts the computer off. When you turn it back on, it loads a fresh copy of Windows from the hard drive, and any errors that might have occurred the day before are not copied. As far as viruses goes, it is a little bit more secure to shut your computer down instead of putting it into hibernate. How much more secure depends on some of your settings.