I have seen some posts with similar title but no one seems to apply to my case. So I'm writing this new post.
I'm working for a nonprofit organization which recycles personal computers.
For the last years we have provided hundreds of computers based on Ubuntu (mainly xubuntu).
Recently we got a set of computers with W7 installed and running. They are using BIOS and msdos partitioning.
As we install xubuntu-12.04 it isn't possible to get access to grub, getting always the 'no bootable device' message. Even I tested with an old 10.04 but with the same result.
From CD/DVD you may boot and chrooting you may work with the installed system (xubuntu 12.04) without any problem.
From this point (my xubuntu system) I reinstalled grub (grub-install) without errors but … the same problem.
I run Boot-Repair (http://paste.ubuntu.com/6964514/) but … the same problem.
It seems BIOS doesn't like to look at MBR or MBR is wrong and I (grub-install) can't change it.
Thanks in advance