As you may know, there are several paid-for partitioning utilities such as Partition Magic and Partition Commander.
In windows there is Disk Management, but for greater capability, I prefer the following :
The free little jewel called GParted--LiveCD
LiveCD, meaning that you build a bootable CD and do your partitioning independent of your OSes.
This will D/L as an ISO file, a raw image file. Leave it on the desktop.
Now you will need an ISO burning utility. Many folks will use Nero (or similar) but there is a free and easier solution called BurnCDCC .
Remember that BurnCDCC can only be used from inside the Windows environment.
D/L it and put it in a place where you can find it quickly. Again, for starters, put it on the desktop. You can tuck it away somewhere later.
Once you have both elements ready, just open BurnCDCC and tell it where the GParted ISO file is.
Then tell it to burn and verify.
Now, with your new bootable CD and your subject machine set to boot 1st from the optical drive, boot to GParted and partition your drive.
Partitioning utilities are very powerful, so have a well thought out game plan before you start.
Keep your eyes wide open when you do this and of course have any valuable data backed up.
http://gparted.sourceforge.net/livecd.phphttp://www.snapfiles.com/get/burncdcc.htmlYou will find BurnCDCC to very useful for other ISO-burning duties, such as burning new Linux distros from the Windows environment.
Edit:
Had I known about GParted, I would not have purchased Partition Magic and Partition Commander.
Hmmm...I could always sell them on eBay
Yet another way to acquire a partitioning utility is to discover your Hard Drive's manufacturer (use Everest Free or PC Wizard) then go to that site and D/L your drive mfr's Disk Utilities.