Why using IE9 Disabling Flash Shockwave improves perfomance considerably?

Have been having really hard time with tabbing, even starting up or shutting down IE9.
So went throgh the Addons and disabled and enabled addons one by one.

When enabling Flash, I consistently get problems everty time, even loading google front page! But there is no flash on google main page, so why is flash is causing problems for a page not requiring flash at all?

The only good point has been youtube having alternate players besides flash, but even on microsoft sites can not view videos although silver light was enabled.

What is the alternative for flash viewing?