For those interested:
To no longer be constrained CPU frequency on windows Vista and Seven with the Athlon 64 or Turion
> In: x:\windows\system32\Driver\ (x is the letter of the hard drive where is located your operating system)
> Delete the file amdK8.sys with administrator rights
> Retrieve the same file amdK8.sys recovered on windows xp
> put it in x:\windows\system32\Driver\
> If the trick worked you will have
(triangular) in Device Manager on the processor
> now download RightMark CPU Clock Utility and use it to adjust frequency and voltage to your CPU needs.
This trick works perfectly on my Amilo A1667G with the Athlon 64 3400+ and Windows Seven.
One thing to say : farewell winXP!