OK. I gave it a last try by cleaning the fans and the heatsink. I saw there was very little coolpaste between the cpu and the heatsink - is that really important? After the cleaning I was able to use the laptop for a few days flawlessly, but then again a freeze.
I don't know if this is good, but then I put the laptop in the fridge, and after 10 minutes I took it back out: the laptop was responsive (touchpad, keyboard) for a few moments and froze again.

Could overheating be my problem?

A weird detail I haven't mentioned yet: after a freeze sometimes the mouse right click and left click reverse, and the keyboard stays unresponsive for a while. After that the laptop works perfectly.

jass,

If you decide to try and replace the system board, you should be able to find instructions on Cpmpaq's ( HP's ) web site. Most manuals can be downloaded. I taught people how to do a lot of that kind of thing, the manuals are necessary. They will show you where the screws are, and the best order to remove and replace parts.

I used to tell my students you need the eyes of an eagle, and the hands of a brain surgeon to work on laptops. After their first experience, no one argued the point.

Okay folks, I know this is an old post, but I recently found out you could stop the freezing by tilting the laptop in a weird position. When you turn it back in its normal (horizontal) position, the freezing continues! Does this sound familiar to someone?

Interesting. It indicates to me something is moving, and causing the problem. It is guess work at this point. Heavy items like the battery, or hard drive are possible candidates.

I would guess the weight shift is causing a broken, or a made connection. Battries and HD's are easily removed, and re-installed. Do one at a time and see if you can isolate the problem. Sometimes just the re-seating of the component will make it work better.

Other than that, have a careful look at the wiring inside the system. You are looking for pinched wires or cables.

I checked all the cables, removed the hard disk (I have already tried without battery: it froze) , and tried my puppy live usb, but still a freeze.

I just installed some diagnostic tools from the hp website (they only work with win xp), and something weird happened. The diagnostics were running (10 loops) , but there was an error concerning the dvd-drive (no media found) so I cancelled the tests and inserted a dvd (I also plugged in a usb and an sd card) and suddenly the system froze. I normally leave the laptop for an hour and the freezing would be over, but now I had to do a hard restart after about 12 hours...
But after this reboot I was able to start the diagnostics again, and now it's running for 10 hours without a freeze!! And there are no errors at all!

It froze again. I've got nothing to do, so I'll spend my time trying to repair this laptop :)

Now I removed everything till I could see the whole motherboard - see this photograph. I booted and waited until the system froze again, and by accident I pressed somewhere and the freezing stopped! This could explain why the laptop stops freezing when you tilt it. I tried pressing everywhere and it's really astonishing: when you press somewhere on the motherboard the hanging stops, but when you release it the hanging starts over again!

I found out pressing on some spots could stop the freezing, while others won't. I indicated it on this photograph: red for working, green for no difference. So I think the culprit should be on the bottom of the picture, or on the backside of the motherboard?
I also had some problems with the screen: I recently got (while freezing) these little stripes on the screen and the laptop suddenly turned off...

I suspect you will have to replace the system board. Pressing on various parts of the board cause problems, probably because the wiring on the board is poor. Printed circuits are moving when you press. It could also be cold solder joints o the board. If the system is worth salvaging, change the system board.

"Okay folks, I know this is an old post, but I recently found out you could stop the freezing by tilting the laptop in a weird position. When you turn it back in its normal (horizontal) position, the freezing continues! Does this sound familiar to someone?"

Umm you've got to be kidding. Yes, like i have been fighting this one for a week.
I took it apart yesterday and found the wifi card was missing and the cable ends
dangling dangerously close to the edge connector for the wifi card. I figured that the
antenna wire ends had brushed up against the wifi edge connector and thats why tilting the laptop (usually tilt to the right) would get the thing working again.
I started getting problems with the USB dropping out.. My keychain would unmount itself.
Then the network started disappearing. I use a pcmcia card.
I love this laptop as I like the trackpoint which are hard to find these days.
Although the thinkpad trackpoint is easier on the finger.
Starting to sound like a bad BGA chip that would need to be HOT-AIR reworked for a permanent fix. (( look up BGA and XBOX 360 ))

BTW in windows my network connection would randomly show 4.9 billion packets rec'd and then flexing the base of the laptop would reset the number to 311 or 3000 etc...
Linux would freeze.. never had it come back. I was able to get the network to stay on for a little while by scaling back the cpu to 800 mhz or conservative. But eventually the PCMCIA
slot would fail and wouldn't comeback.. dmesg would show failure to power up pcmcia.

Anymore clues?

I am probably just going to get another one off of ebay and use this one for parts..

I am going to be getting a 250 watt hot air station anyway maybe I'll give that I try at some point.. argh..

Duane

Duane,
I recently found a new motherboard for this laptop, and replaced the old one by it. This worked for a few months, and then... the laptop started to freeze again! I think the problem is the laptop gets damaged when transporting, since I mostly take him along in my backpack and the laptop is quite flexible.

I also posted this on the HP forum:
http://forums13.itrc.hp.com/service/...readId=1077508

Even with this new motherboard it started to freeze after a while, so I think the motherboard gets damaged when loaded, and nothing can be done about that - except a new mobo.

I have purchase another NC6220 off of ebay.
I believe the BGA chip(s) have failed, causing the intermittent connection problem.
I've seen enough of these kind of chips fail on consumer type goods.
My son picked up a Xbox 360 last summer for $30 that had the Red Ring of Death.
He first tried the 'wrap it up in a blanket and run it trick" that worked for a while but
was still intermittent he has since used a heat gun to 'reseat the chip' and now has extra fans keeping the case cool..

The links below explain it better than I can.

http://en.wikipedia.org/wiki/Ball_grid_array
http://www.youtube.com/watch?v=t8o6awjbWZw

When I get my rework station I will be reseating the chips to see if that helps..