On my old (2007) HP pavilion the CPU was swappable. Just for the sake of science i downloaded the dismantling manual and took it apart (for no real reason other than it was getting old). 3000 screws and 3 hours later i got to the chip, surprisingly it wasn't soldered onto the motherboard and was in an interchangeable socket. Then i threw it in the bin!
That particular laptop came with an AMD cpu, but could be purchased with various AMD CPUs depending on how much you spent. Goto the manufacturers website and have a look at the laptop in question, if it says this laptop is available with CPU A/B/C then it's most likely swappable.
I personally would never do it unless it was out of warranty, i'd rather just buy a new laptop

. It is good fun though!