I have a Lenovo ThinkPad T410. When I bought it, about two years ago, it had Windows 7 Professional installed. I installed Ubuntu 12.04 LTS from a bootable flash drive "Live" system as a dual-boot system. Everything worked properly, and I've been happily using it ever since.
Today I tried to upgrade it to Ubuntu 14.04 LTS. The last time I upgraded Ubuntu, on an Acer netbook, something went wrong and I wound up reformatting the drive and making a fresh install. This was only a minor aggrevation, since I had backed up everything.
Because I need to keep the Windows 7 available, I made another bootable flash drive. I booted from it and chose to install Ubuntu. The very top option was to have Ubuntu 14.04 replace Ubuntu 12.04 and keep Windows 7. This was exactly what I wanted, so I selected it and proceeded with the install. Everything appeared to go normally. When I got to the end I got a screen message that the computer would have to restart for the changes to take effect. I expected that, and clicked to restart.
When the laptop restarted I did not get my expected boot menu. Instead, I got a completely blank screen with white letters in the system font:
error: file not found.
grub rescue> _
I booted from the USB again and went through the same install procedure (it did report that Windows 7 was still there). Once again, it appeared to go normallly, but when I restarted I got the same error.
Is it possible to "repair" Grub? Can it be re-installed from the bootable usb?
Most importantly, is there a way to save Windows 7?
Thanks in advance.