Can I upgrade my laptop's Intel i7-2670qm to an Intel i7-2820qm?

If you can find a Pavilion DV6 model that has an i7-2820qm, then it is possible. You would then need it open up your laptop to determine if the CPU is soldered into the motherboard or not. If it is soldered, then it would be pretty difficult even if you are an expert solderer.

To me, it is not worth the trouble and cost to install a CPU that is only 200MHz faster and has an additional 2MB of cache.

think so , if it was offered in the comp or is the same chipset on mb sure , not hard at all . look at my sig , HP laptop came with t-7200 20 minutes later it had x-9000 in it , simple swap .

But I don't think you'll get a big boost in performance , might not be worth it unless cpu was free . I my case went from 2.2 to 2.9 + with bigger cache/ smaller die size less heat , you will no gain much

If it was a custom built job such as Clevo, I'd say yes...... w/ HP, it's very unlikely.

General rule of thumb, don't try and replace components in a laptop.

Actually unlike the rest of the people here who likely have never own or tried to upgrade a laptop I have upgraded mine. Intel laptops can be upgraded depending on the model and if the cpu isn't embedded. 200mz and 2mb or extra cache isn't worth the extra expense but if you are really hurting for the extra performance than go for it. HP didn't put any seals warranty wise on my laptop so that made things easier when I did mine. You may or may not have the same luck but you will have to find the service manual on HP's site before you do any thing. As for the board I learned first hand that they are not unique to each model.

Very wrong ! I have changed cpu's on many HP Dell and Asus laptops , takes about 20 minutes . As long as it came on a like model or uses same chipset , memory it will probably work .