So the soldered RAM can run 1066mhz?
Do your everyday activities, and see how it feels. If it feels slower, then you have a problem. But really, you shouldn't be able to see a significant difference between 1066mhz and 533mhz.
EDIT: I did some googling, at it seems it does run at 1066mhz. That means it should allow the 2gb stick run at 1066mhz too. Are you sure that Corsair RAM is 100% compatible with your netbook? This could be another reason why the speed is halved.
EDIT 2: Ok, after some more research, it seems the soldered RAM can run at 1066, but HP's BIOS purposely locks it to 533mhz. In other words, your system is already running the RAM at the max speed the BIOS allows. You can't do anything about this then...