Simple answer (for linux newbies): There may be multiple probable causes to your problem. It depends on many factors that you didn't cover. How did you created the linux partitions, how did you install Install Ubuntu? From LiveDVD? From LiveUSB? Manual or automatic? Does your PC have a BIOS or a UEFI? Is your partition table an MBR or GPT? Etc. I know all these questions scare you. It did to me too, a long time ago when i started learning linux.
First, Windows will never recognize ANY other operating system. That's the Microsoft way. Or any other partition types except their own. Windows, bootloader (winboot) will never recognize any other bootloader.
Secondly, Ubuntu (as well as other linuxes) will always recognize other operating systems like Windows and MacOS. Ubuntu's bootloader (GRUB or GRUB2) will always recognize winboot.
Every operating system needs a bootloader - a small software that tells the PC hardware the identity of the operating system, how it works and how to load it into RAM memory. An installed operating system without a bootloader is useless, because it will never be recognized by the hardware.
What happens when we install multiple OSes (each one with its' own bootloader) on the same PC? Well, one bootloader must rule them all. A single GRUB is sufficient for multiple linuxes. For a Windows + a linux PC, a winboot must be present and a GRUB too. Preferably on different partitions (because if one fails, at least you'll have the other still available). But the GRUB must be the ruler, because it recognizes any other bootloader, and winboot does not.
How to make GRUB rule the world? First install Windows. Automatically. Don't erase/merge any partitions. Secondly install Ubuntu. During Ubuntu install process, it should recognize the Windows installation. Choose install Ubuntu along Windows option. When asking you where to install GRUB choose
/sda. That means the root of your first hard-disk. Highest priority possible! Don't choose any /sda1, /sda2, etc, because that means installing GRUB in the root of the specified partition 1, 2 ,etc and may result in conflict with winboot, erase winboot or not superseding winboot.
One last thing: Although it is sometimes possible to install Ubuntu to NTFS or FAT partitions, that is only advisable to advanced and expert linux users. Any typical linux (Ubuntu included) needs AT LEAST 2 partitions: a swap partition and an ext2/3/4 partition.The swap partition is always inaccessible, it acts as virtual RAM memory, the ext partition is where your Ubuntu will be installed. For adequate usage SWAP size should be = (1.5...2) x RAM size. EXT partition can be any size you want, but no less than minimum size recommended by Ubuntu.
Tip: The Windows' Disk Management equivalent in Linux is called GParted. And you can use it before (as in liveCD) and after you install Ubuntu.
For proper viewing of ALL partitions on your disk ALWAYS use GParted!! A had an unpleasant surprise with Win8: it automatically creates a recovery partition upon install that is not visible in Disk Management, but is recognised by GParted!