K got it.
Tableau Server ignores hyper-threading, when counting the no. of cores.. So my laptop has only 2 cores which logically appear as 4 cores.
Tableau Server 8.2 would allow you to proceed with the installation even if this criteria wasnt met. But 9.0 doesnt allow you to start the installation.
Thanks for providing an answer. I'm sure this will help others!
I had run into this with the Beta testing of V9.0. Tableau support had instructed me to install the 32 bit version of Tableau server on my PC.
Install the 32-bit version as suggested and you'll be up and running.