Hp laptop with ati hd3200 screen going blank

3 year old HP DV5-1004nr laptop with Vista. Recently I have had a problem where the screen randomly goes blank and keyboard appears to be locked up (ie. I can't put it to sleep with Fn F5). Backlight is still on, but screen is totally blank. I have to do a forced reboot to reload Windows Vista. Sometimes it works for hours....sometimes it won't get to welcome screen. Doesn't seem to be heat related as it happens when laptop is cold or warm.

This happens randomly. Sometimes it happens 2 or 3 times a day, sometimes it will go 2 or 3 days before it locks up. I use Firefox mostly but also Chrome and IE9. Seems to be no correlation between a particular application and locking up.

I am running latest BIOS, regularly updated Vista and latest ATI video driver. Tried rolling back driver, tried system restore. I seems like it is a software problem. Have tried just about everything but still have the problem. Not sure what to do next.....any ideas?

Does it do this while you're actively working on it or do you come back to it and find it frozen? If the latter then consider changing your power settings so it doesn't go to sleep. I had a prob with a Vista laptop locking up after going to sleep a few years ago and to fix it I beat up the ACPI part I think.

If it locks up while you're using it but you don't feel hot air or the fan on max then check if your cpu air duct is cleared. I had a laptop a year ago which crashed all the time but didn't seem to be reacting like it was overheating. When I opened the cpu compartment I saw what appeared to be a half a sock's worth of lint occupying the airflow channel. I imagine the user used the laptop on their blanket or sock pile regularly.

I had a laptop that froze every xx seconds consistently without skipping a beat and removing the battery fixed it so maybe in a moment of desperation you can try to see if it's bad battery related (unlikely but why not).