Mobiles are usually cheaper...they fit in socket A because they ARE socket a simple as that. If it's the same socket it'll fit. There's no such thing as a 'mobile socket a' socket and a 'desktop socket a' socket ya see what I mean? When I bought my 35w 2400+ XP-M it was $87 at newegg but last time I checked it went up to $98. You can get quite a bit of overclocking out of these atleast 400MHz extra to bring it to 3200+ speeds which that chip is twice the cost.
why not build all chips to run at half the wattage if they can produce same performance?
Ya know I really don't know that. They build the laptops with half the wattage simply because the Laptop wouldn't be able to put out enough power for a 65w chip and besides that it keeps it cooler. Why they simply don't make desktop chips at 35w I'm not entirely sure. I'm sure they have some reason for it, but it would make sense to make a 35w desktop designed chip I suppose.
You still never answered my question...WHAT MOTHERBOARD DO YOU HAVE?
Beyond that, if you really want to overclock yes go with a mobile. the 2500+ XP is also another noteworthy overclocking chip, but overall I say either get the 2400, 2500, or 2600+ XP-M and make sure you get the 35w not the 45w because they do have seperate ones like that. The 2400+ XP-M has 512k L2 Cache compared to the desktop version, 2400+ XP only has 256K L2 Cache so that's a nice bonus. Default of 2400+ XP-M is 1.8GHz and 2400+ XP is 2.0GHz, but the XP-M reaching 2.0GHz is like a walk in the park, that's not even a challenge for it. Getting it stable at 2.3 and 2.4 is where it starts getting a little more trickier.
it lets me overclock some, up to 132*12.5(the multiplier)... but beyond that it is no good, and the memory is not holding it back, so i dont know what is wrong.
Your chip isn't designed for OC'ing in mind man, so I'd really stop trying to push it before you wind up actually frying it. Yes you technically can Overclock ANY chip, but certain ones are better for it and yours definitely doesn't rank in that club. If anything I'd just try to do what I did. I had a 2400+ XP so I just bought a new mobo and the 2400+ XP-M and built a second system using my old chip and motherboard...obviously I had other spare parts lying around to be able to build that 2nd machine, but I'm just saying it's an option