Most of the vendor shipped desktop/Laptops comes with a single partition drive named C, which is a great bottleneck to have dual boot.
Partitioning an existing drive can be possible through different commercially available Partition Magic software but for that one needs to shell out some bucks.
We can achieve this sort of partition using some reliable and easily available open source tools.
Knoppix which is a bootable Linux Live CD which contains most of the GNU/Linux tools can provide a handy approach to achieve the partition.
* Get Knoppix iso and burn it to a CD.
* Boot from Knoppix on the machine which needs partition.
* Run QTParted, that will open a window showing the existing partition.
* Right click on the windows partition, choose RESIZE
* In the text box labeled FREE SIZE AFTER, specify the size of which one want the new partition. This will create free space of specified size.
* Right click on the free space created, click create.
* Select partition type, click OK.
* From file menu, select commit. This will make the partition change persistent.
* Restart the computer.
* Boot into the existing windows.
The above steps will eventually make another partition of specified size.
make world open.