I use a 'by hand' speed calculator -- not a reporting mechanism. The speed is being reported correctly in the range of 1000-1300 MHz, usually about ~1200.

Forewarning: This post has a bit of a condesending tone. I appologize for it, but I find sometimes the direct 'I have it plugged in and am insulted you're asking' response can get me to a fix faster than politeness.

My CPU is constantly at 100% as a matter of course. I run a few different heavy computational tasks on the system (large compiles, prime number factorization, etc)
In addition, I use speedswitch and a few other programs to ensure that the Windows OS is instructing the CPU to run at full capability no matter the scenario. The calculator I use does fully stress the CPU calculator -- I am not some benchmark worrier who right clicked properties on whim, it took seeing a sudden and significant slow down in basic tasks (including graphics renders, compile work, and overall system use such as opening applications like Opera and Word) before I even started checking for the cause. The byhand calculator I'm using was handwritten to do some basic, pipelinable loops for a Pentium4 architecture at high speed and compared to other systems of its calibur (including another laptop of roughly the exact same build) to ensure accuracy. It has been confirmed by the Windows OS and various applications that measure speed with their own routines (incl. speedswitch)

The system is visibly slower, both in use and via reporting mechanisms.