After installing Ubuntu, Windows didn't boot so I installed boot repair to fix this problem. But I am getting the message displayed below.
I tried to make a new partition with unformatted file system but still receiving the same message.
How do I fix it?
First you should check if booting the system as MBR/BIOS instead UEFI is really what you intended.
The following is a quote from Is it still possible to install Ubuntu to an external harddrive with UEFI? which is about several ways of setting up bootloaders and necessary partitions. Refer to the original answer if some of the instructions are unclear (it would have been very repetitive to explain almost the same thing in detail 3-4 times).