I'm working on a friends laptop which I thought had a Mobil Celeron CPU. It ran at something like 2-2.4GHz but then dropped down to 1-1.2GHz when idle.
Are you sure it's a Celly? If it's in pieces can you see the sSpec code on the proc (ie SL6FG, SL6QH, etc)? That sounds like the early implementation of Speedstep on the P4-M:http://en.wikipedia.org/wiki/SpeedStep
For example, a Pentium M processor marketed at 1.5 GHz can run at any speed between 600 MHz and 1.5 GHz, at 200 MHz increments, using SpeedStep III.
However, older processors have fewer increments, such as the Pentium 4-M. For example, a 1.7 GHz Pentium 4-M can run at 1.6 GHz, at 1.2 GHz, and at 786 MHz.
However I never saw my P4-M run at 768MHz.