Socket P looks like you can move up to a 925 which is .1ghz faster. Also the Intel Celeron 900 should be 2.2ghz.
You need to go to the manufacturer's website to determine what socket p CPU the laptops can use. Just because the CPU can physically fit into the socket does not automatically mean it will work. If the BIOS is not updated to recognize the CPU, the CPU might run at the lowest speed or the laptop may not even get past to post screen.