I bought an Acer laptop with Win7, and installed Linux Xubuntu as second OS. It says the GRUB was installed as well, but at the boot it keeps loading only windows. No grub screen at all.
What to do?
Run Xubuntu from LiveCD or LiveUSB and install Boot-Repair.
To install Boot-Repair, open up a terminal by pressing Ctrl+Alt+T and type the following commands:
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update sudo apt-get install -y boot-repair && boot-repair
After installation, Boot-Repair will automatically launch. Now select "recommended repair" to repair grub.
Reboot and that's it.
You should now have a Grub menu on boot allowing you to choose which OS to boot.
You might be able to get windows to chainload linux with easybcd, assuming that grub was installed somewhere. Usually grub gets installed and overwrites ntldr/bcdldr, though some install options let you pick with partition to install it to.