How to fix and restore firmware?

I own a iPod Classic 5th Gen Video and have been getting many problems with it with connecting it to my PC or having it to work properly, I find that it likes to lock up quite often. I've tried to use iTunes and it doesn't see it. How do I fix/restore the Firmware manually? I've read somewhere that you can put it into a recover mode where you can place an update file on it and then it will do the rest and hopefully this will fix it.