Not sure how much help this is, but it appears that your specific HP was a model that wasn't recalled for issues such as this. According to posts in the HP support forums, certain models in the 6700 and 6800 lines were recalled for various issues relating to the NVIDIA graphics. Other models weren't recalled and aren't eligible for free repair by HP. It appears to me that the dv6700 was not lucky enough to be one of the recalled models although it is plagued by many of the same overheating, freezing, and random shut-down issues as recalled models. 

@ Lisa,

Coupla' things on your problem.

First, since your HP laptop is 5 years old, I agree with Jim, you might consider 5 years "is a pretty good run and just cut your losses." I'm not saying that you should necessarily make a boat anchor or a door stop out of the thing, but at this stage you have to consider the cost analysis of paying to get it repaired (that may not even be possible, and you'll be throwing good money after bad anyway), and you may be feeding oats to a dead horse. At 5 years old (which is an eternity in the computer world), I definitely wouldn't spend a lot of money on trying to get the thing operating properly.

The average "TTF" ("Time to Failure") of most laptops, especially if there is not some mechanism used to extend that life (more on that in a bit) is about . . . drum roll . . . 5 years. Some live a lot less, some live a lot more, but that is the average.

The money you would spend on this thing would be better spent on a totally new machine. For what you spent on this thing 5 years ago, you can now (for the same price or even less) get a machine with a much more powerful CPU, probably 4GB of RAM, and at least a 500GB HDD, probably bigger.

OK, that's one thing: DO NOT spend a lot of money, if any, on this dinosaur, and consider getting a new machine.

Now let's deal with the possibility of a low cost or FREE remedy.

As Jim said, the problem may have either a hardware or software solution. I'd try both together.

Computers hate three things: Heat, Dust, and Vibration. (It's always amazed me that cars nowadays use computer chips ["EPROMs", " . . . Programmable Read Only memory", I forget what the "E" stands for]. What the heck do you have under the hood of a car? Yes, Heat, Dust and Vibration!)

Let's take Heat and Hardware first. In a laptop, you have a reduced volume of circulating air because of the small case. Consequently, laptops are more prone than desktops (which have a larger volume of circulating air) to heat problems. That's one of the main reasons that the average TTF of laptops is much shorter than the average TTF of desktops,

Heat can be enhanced by dust, as Jim said. I'll deal with cleaning in a second.

But the first thing you may want to try is a chill mat. Chill Mats are specifically designed to provide additional cooling for a laptop . . . typically with a fan circulating air UNDER the laptop. A good Chill Mat will reduce the operating temperature by maybe ten degrees, and hence if one is used from day one, may extend the TTF of a laptop well beyond 5 years.

I had an HP laptop, ZE4700, (still use it now and then, even though it's a huge dinosaur) and used a Thermaltake Chill Mat and it's still going strong. My main machine now is a Dell Laptop, and I also use a Thermaltake Chill Mat with that.

There are a gazillion Chill Mat brands out there. Google "Chill Mat" or go to a vendor like Tiger Direct. I have had success with Thermaltake, but there are plenty of good brands out there. For example, I used a Targus Chill Mat for a while, and that was a good one too.

My recommendation: Not any particular brand, but rather specs. Preferably, you want to get one that's either aluminum or some type of light weight metal. A lot are made out of plastic . . . plastic will crack eventually under the weight of the laptop.

Get one with either one big fan (Thermaltake), or two fans (Targus). Some advertise three fans . . . I've not had success with those . . . they have been noisy, and the three fans, to fit in the footprint, are wayyyyy too small.

You can get some for $10 bucks or less. I tried a few cheapos, and proved "you get what you pay for". The things failed quickly. About $30 or $40 bucks seems to be the right price range (I think my Thermaltake was about $40 bucks.)

Now on cleaning. Compressed air does wonders. BUT, be careful. Most laptops have some kind of vent in the side or back, sometimes two vents (intake and outflow), and the vent is where you want to put the burst of air. However, usually directly behind the vent is the fan. If you squirt the compressed air in the vent, you take the risk of spinning the fan so much that you'll ruin the bearings on the fan. To avoid that risk, simply place something like a Bic pen plastic ink rod in the fan blades (through the vent) so that they are immobilized while you're giving the space a burst of compressed air.

Of course, you can always crack the case and clean that way, but I'm sensing maybe you don't want to go that far. Cracking the case on a laptop can be a pretty daunting task.

Now on software, I see that some of the posters in this thread have already given you some ideas. Jim's caution on SpeedFan is good advice. There are others out there that, while not quite as comprehensive as SpeedFan, are good too. Just Google the things ("cooling software" maybe) and ask here if you have any questions on cooling software.

So, the summary:

1. Consider purchasing a new machine.
2. DO NOT spend a lot, if any, money on getting the old machine operating normally. If a Chill Mat doesn't solve your problem . . . STOP, that's enough money.
3. Whether you try to save the old one or get a new one, USE a Chill Mat no matter what.
4. Try FREE cooling software.
5. Keep the machine as free of dust as possible.

EDIT 4/28/2012: All this assumes heat IS indeed the problem, which as Jim said, is a BIG assumption and mere speculation. All bets are off if heat IS NOT the problem . . . a real possibility. Who knows?