Written by Greg Kjono
There are a couple of hidden files that typically use up a lot of disk space, especially in systems that have large amounts of RAM. These are the pagefile.sys and hiberfil.sys. Hiberfil.sys can be deleted if you don't use the hibernation feature. Instructions on how to do that are available at http://nerdsknowbest.blogspot.com/2013/01/how-to-delete-hiberfilsys-on-windows.html.
I don't recommend completely removing the pagefile, especially on desktops and laptops, however. You can configure them to not use so much disk space though. By default they are set to "system managed" and are probably close in size to the amount of memory you have in your PC. Chances are that you aren't actually using most of that space in the page file, and that your computer is just allocating that space in case it needs it in the future.
There is a slight perfomance hit everytime your pagefile needs to expand itself, and that's the tradeoff of starting it with a smaller size. However, if you have a lot of RAM, you probably won't be using the page file much, and therefore it won't have to expand very often. This performance hit probalby won't be noticible to the average user either.
To change the size of the page file, right-click on "Computer" or "My Computer" depending on what OS you have. This is usually located on your desktop and/or your start menu. Then click on "properties" from the menu that opens up. If you are running Windows 7, Vista or 2008, click on "Advanced system settings" on the left side of the window that opens. Windows XP, 2000 or 2003 users just need to click on the advanced tab. Click on "settings" in the performance section, and then click on the advanced tab. Next, click on the "Change..." button in the virtual memory section.
Uncheck the box that says "Automatically manage paging file size for all drives". Select you C: drive from the drives shown, and select the "custom size" radial button. I recommend setting the "Initial size (MB)" somewhere between 512 and 1024 (set it to a number divisible by 8). If you only have one hard drive in your PC, then set the maximum to recommended amount shown towards the bottom of the window. Then click "set".
If you have multiple hard drives, you can split this up between the drives by selecting each of the drives and configuring the "Custom size" on each of them. If you do that, just split the maximum size between the amount of drives you are putting a page file on.
When you are all done, click "OK" through all of the screens. It will warn you that you need to reboot before the changes take effect, and give you the option whether to reboot now or at a later time.
You can also you this method to completely move the pagefile to a different drive if you want, but doing so will eliminate the ability for your system to create dump files that can be helpful in troubleshooting issues.