What operating system did you have before you switched to Windows 7 and did it say the right specs when you had it? Also I found these on the Cpuid website on the CPUZ part-
Q1: CPU-Z reports my CPU running below its clock specification or the clock speed is varying.
A: This is the effect of the CPU power reduction mechanism : C1E (Enhanced Halt State) and/or EIST (Enhanced Intel SpeedStep Technology) for Intel CPUs, Cool'n'Quiet and or PowerNow! for AMD CPUs. Load your system and you will see the frequency increase to its nominal value.
Q2: CPU-Z reports a wrong CPU vcore.
A: Please download HWMonitor then save monitoring data (menu file -> save monitoring data) and send back the file to that address.
Try that and see if it works