No such thing as a silly question
Your most important data should be stored there first, this may include family photographs, business/legal information, videos and music files and anything else that you cannot replace.
ASUS software taking up 2GB of space on your HDD sounds a bit excessive, can you post an expanded screenshot of Disk Manager for us, see my canned text below;
Can you post an expanded screenshot of Disk Manager which you can access by pressing the WIN and X keys together on your keyboard, alternatively from Windows 8.1 update you can right-click with the mouse or stylus on the Start button to bring up the menu.
To capture and post a screenshot;
Click on the ALT key + PRT SCR key..its on the top row..right hand side..now click on start...all programs...accessories...paint....left click in the white area ...press CTRL + V...click on file...click on save...save it to your desktop...name it something related to the screen your capturing... BE SURE TO SAVE IT AS A .JPG ...otherwise it may be to big to upload... then after typing in any response you have... click on browse...desktop...find the screenshot..select it and click on the upload button...then on the lower left...after it says upload successful...click on add reply like you normally would.
Screenshot instructions are provided to assist those that may read this topic but are not yet aware of the “how to”.
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