I have a lenovo z570, and I installed Ubuntu 12.04 alongside Windows 7. Recently all my games that I've been playing stop responding due to a AppCrash.
I searched for the error on Google and they said it had something to do with Ubuntu. So I deleted the partition. After restarting my laptop i get the "unknown filesystem" grub rescue error.
I tried using a windows CD to boot, but it can't.