Compaq R4000 crashes on hibernate

I have a Compaq Presario R4000.
When I close the lid, sometimes it hibernates ok but sometimes the screen goes off but the processor keeps going. I know this because when I lift the lid to use it again the screen is black, but everything is still running and the only way to use windows is to manually power off and power back on again.
Can anyone advise if this is a hardware problem or a software issue? I am thinking of upgrading to windows 7, but I am not sure if its worth it or if I should wait till I just buy a newer laptop.

 

As directed by DavidGP, THE HIBERNATION ISSUE was a problem I remember withXP Professional- If you shuffle your finger over the mousepad-does it come on ?
Otherwise, as DavidGP says, just lightly pres the start button once, does it come on ?
Unfortunately screensavers can use a lot of battery, o unless you have power supply attatched , you could be shut of when you need it, if out somewhere, otherwise use the windows moving logo, as that does not appear to use too much power.

 

Hi Guys thanks for replying.
I am using XP home edition. Version 5.1.
When my laptop does not automatically respond to the lid being opened to come out of hibernation, a quick press of the power button or tap of the space bar will wake it up. But the issue I am having is that it does not seem to go into hibernation properly at all on occasions; the screen will go blank as if the hibernation process is initiating but it does not completely hibernate as the fan/processor continues to whir away. When this happens there is no way to either properly shut it down or wake it up, it seems 'locked' in this state.
It behaves like the screen has powered down as it would if the power settings had triggered a monitor 'power down', yet it occurs only seconds after closing the lid and then will not respond to any input on the keyboard, mousepad or power button.
It seems to occur about 30% of the time but interestingly, when it does happen it sometimes goes through spates of recurring and my gut feeling is that its as if a background (scheduled) process needs to run and is interrupting the hibernation. I don't think I have any scheduled processes though - it doesn't seem to have anything to do with my antivirus software. I eliminated this some time ago by uninstalling AVG free and using Avira instead.
Sometimes it works perfectly. I would think its best to shut it down each time rather than close the lid and hope for the best because I cannot imagine it is healthy for the laptop to manually power down so often. Do you agree with this?