Wd2500u017 Issue

My apologies to the HelpOwl staff for this near duplicate post. I meant to amend my original answer and did not realize I didnt click edit but "I know that answer" instead.  I chose to change my first answer to this post since I wasnt happy with my efforts anyway. It was an accident. If I could delete this duplicate I would have. I can only change it, sorry.

See if that harddrive is either partioned into a smaller virtual drive or if that missing space is unallocated. That may very well be the recovery partition or if it shows to be unallocated space that may be where the recovery partition may have once been. Is it a single hard drive rig but shows a C drive and a D drive? If so that space is set aside for the D drive and holds copies of the original system files in case you ever need to reinstall the OS.

If this proves not to be the case and the space is just plain missing you can download a program like windirstat or belarc advisor to give you detailed information and visual cues as to what is on and going on with your drive and every other aspect of your rig. Honestly I would reccomend that you download them both because each has its strengths. Windirstat uses visual imagery to show what is taking up disc space while belarc gives you every detail about more than you can think of. Like if you are missing any hotfixes and what if any unsecure ports are open, even your product keys.

http://windirstat.info/download.html

http://www.belarc.com/Programs/advisorinstaller.exe