I have a HP 7935 with XP. This is my "back-up" machine. I haven't used it for several months. When I recently tried to turn it on, it wouldn't work. When I unplugged and replugged the power cord, a green light flashed and went out. Does the computer have a reset or a fuse?

   You say that it will not work.  What do you mean by that?  What happens when you turn it on?

It will not turn on.

   Are you saying that when you press on the power button nothing happens?  No lights, no noise, nothing?  If so, my guess would be that it is a bad power supply.

You are correct.  Nothing happens.

is there a battery that might be bad?

There is a battery that allows your computer to remember what time it is among other things.  If the battery is bad, the time will be off but your computer will still start.

Ray:
Thanks for the help. It was a bad power supply. I bought  new psu and tried to install but it was too deep for my unit. I could have gotten it in by cutting away some of the sheet metal which supports the cd and floppy drives but was reluctant to do that. The common psu available is 5.5" deep and my unit was 4". A friend  that spends too much time picking stuff up in others rubbish had a box full of psus. One of them had the right dimensions. I installed that psu and everything worked fine. The price was right, also.

Good job.