Windows 7 32bit slow performance Cuda app runs 20% slower on 7 than vista


Have just decided to install 32bit Windows 7 pro on a machine that previously had Vista 32bit. The Vista installation was unstable and had unexplained crashes and long dead times at startup. The Windows 7 appears much more stable so far. HOWEVER, the Win 7 install runs my application a good 20% slower than it did and the whole things feels that bit more sluggish or muddy. Really odd that for the same hardware such a big difference could occurr.

Obviously the NVIDIA driver is now slightly newer for win 7 and I am using Cuda v3.0 when before on Vista it was Cuda V2.2.
The compiler settings are the same except if refers to a Cuda V3.0.

Im using a upto date Novatech X1 Pro laptop with a Clevo M980NU motherboard, including dual GTX280M GPUs.

Any immediate thoughts as to why this might be the case?