I am having Acer aspire 4755. I initially had windows7. But tried Ubuntu 12.04. It was working fine. But when I tried to install Windows 7, i got this grub error. I am sure, I must have screwed up the grub file. So when I tried to run a live USB, DVD of Ubuntu back again to install Ubuntu , I got this error: panic occurred, switching back to text console. I even can't install Windows 7 with its starter CD. Kindly help me to remove Ubuntu or remove Grub and get my windows 7 working. I know I have to get the grub working, but how.??