I have encountered this problem on my notebook (with pre-existing Windows 7). Initially, I wanted to install Ubuntu 14.04 alongside Windows, and the Ubuntu installation went well.
However, when I wanted to access Windows, I could no longer do so (Ubuntu works just fine). So, I did some googling and found the Boot-repair ISO file and did a boot-repair. It was shown that the boot repair was successful, but when I restarted my notebook again, I was met with "BOOTMGR is missing".
My boot details is as follows: http://paste.ubuntu.com/8049879
I'd still like to have access to both Ubuntu and Windows 7.