Please advise, as I have just received a replacement for my previuos Laptop which was a Tosh Satellite with a T5500 intel processor.
My new Laptop has an intel core 2 duo T5450 processor rather than a intel core 2 duo T5500, and I would like to know whether the lower intel processor (T5450) would be same or similar and would not make much difference to the laptop operation speeds.
Will there be significant change in performance with the earlier T5450 rather than the T5500 intel processor?

There is basically no difference in performance between those 2 processors. There would be no difference in performance.