How to create a new partition from single volume in windows
If you want you want to install two operating systems in your computer or laptop then you require an empty second partition to dual boot your PC from both the operating systems.
For example if you have windows XP pre-installed in your PC and want to install Windows 7 or if you have windows 7 in your PC and want to install windows 8 consumer preview for testing purpose. One thing to remember that you can only dual boot if you have same bit version of windows as your older windows e.g. if your older windows is 32bit version then you require newer windows of same 32bit.
The partitioning doesn’t require any special training or knowledge you can easily make partition using windows disk management utility that is inside control panel, you can also easily reach to it by right click on My-computer icon then click on manage if ask for administrator password then type your administrator password. Now click on disk management to invoke the disk management utility or open control panel in windows 7/Vista type disk management in search panel; you can also open this utility by typing diskmgmt.msc in run command and press enter to invoke.
In disk management you can view your all hard disk volumes, typically for computers manufactured from dell/hp/lenovo etc. you will found a 100mb hidden partition for system reserve files that keep windows boot files, boot loader etc. that is inaccessible, another one is recovery partition that is pre ship with your computer to restore your PC in case failure of your PC, you can restore your operating system and drivers as like it come from factory. And you will found C: drive that is having your windows OS.
If you want to install other windows OS then you have to partition your C: drive to make room for new windows. How to make partition from C: drive without disturbing you existing windows OS, files and programs- In disk management right click on C: drive and click on shrink volume and will take some time to calculate how much space is available for shrink. Now select your new volume size by typing in numerals and click on shrink, now a free space will be created as the size mentioned by you.
Now right click on free space and click on new simple volume. Now click next, select as NTFS file system and select your drive letter as you desired, also check on quick format now your new volume created and you are ready to install dual boot operating systems in your computer.
You can also extend your partition, right click on C: drive and click on extend and the earlier free space created will again merge to C: drive. Extending and shrinking have some basic limitations. You can only shrink a partition if it has enough free space, and you can only extend a partition if it has unallocated space to the right of it on the same drive. You’ll see empty, unallocated space to the right of a partition if you can extend it. Windows can’t extend a basic partition to its left; you’ll need third-party software for that.
See the picture below for more details-
The situation when you are not able to shrink your C: drive- Actually when your computer is new and fresh , your hard disk’s clusters and cylinders are congestion free. At that time you have more space to shrink your existing partition. But when you have used computer for some time and install lots of program, saved a lot of files then you are not able to shrink partition even you have lot of space free (may be 200GB or more). The another reason that not allow to shrink the partition is some immovable system files e.g. hibernation file, page file, system restore images, error log memory dump files etc. that not allow to shrink the partition. 
How to shrink the partition in this situation – To absolutely ensure that you can shrink the volume, you should disable as many of the system files as you can, at least temporarily. Here’s the list of steps:
- Run the Disk Cleanup Wizard, making sure to remove the hibernation file and all restore points.
- Disable System Restore
- Disable the pagefile (Open up System in Control Panel, then Advanced System Settings \ Advanced \ Performance \ Advanced \ Change \ No Paging File.
- In the same Advanced Settings, go to Startup and Recovery \ Settings and then change the Write debugging information drop-down to “None” to disable the kernel memory dump.
- Disable Hibernation mode in your power options \ advanced power options screen.
- Reboot the machine, and then delete your c:\pagefile.sys file.
- Also defragment your hard disk using Auslogics Disk Defragment tool that is more powerful then your computers in built defragment tool. (for downloading Auslogics and to see how to speed up your slow PC in 15 minutes see my previous post)
Now that we’ve deleted almost every system file that we can, you should run at least one of these free defrag utilities, but preferably all of them, in order to move all of the files to the beginning of the volume, so we can force the Shrink volume feature to work. At this point you should be able to shrink the partition, at least a decent amount. Once you’ve gotten the partition shrunk, you should re-enable those important files:
- Re-enable the Pagefile (Reverse instructions above)
- If you have issues re-enabling hibernate, follow these steps.
- Enabling System Restore or kernel debugging information is entirely up to you.
- Reboot.
Resources – http://www.howtogeek.com/101862/how-to-manage-partitions-on-windows-without-downloading-any-other-software/