Im not sure about this but does Intel have a version of AMD's Cool N' Queit? It could be that, if your processor isnt under load it will slow down to save energy and keep it cooler. Not sure if intels have this or not.
EDIT: I just noticed you are using a laptop so thats probably it.
The Amish computer:
AMD Opteron 165 CCBWE 0551@ 2.25ghz(250 x 9) 1.45v cooled w/ Thermaltake Big Typhoon | DFI LP Ultra D | eVGA 7800GT@ 465/1110 | Sound Blaster X-Fi XtremeMusic | 2GB G. Skill DDR 500 @ 250mhz 3-4-4-8 | 80 GB SATA + 40GB SATA + 200GB IDE| 480w Thermaltake Silent purepower | Thermaltake Tsunami Dream case (Black) | Windows XP Pro |