On the top of of the KBoard there is a silver oval with the center oblong button I have used OK for year to start/stop this laptop. A few days ago, attemting to speed up this box I removed some programs (Ctr Panel). Mistakenly, removed also the Twister display driver. However, was able to reinstall in (Device Manager) from the web. But, I cannot stop/hibernate any longer as pushing the indicated button has no effect. I am afraid to close my laptop for fear that I'll never be able turn it ON again. What should be done to reactivate this button?

Thank you