Free Space on a WD 2 TB External Drive keeps decreasing

Dear experts,

For some reason, the available free space on one of my external HDDs (Western Digital 2 TB) keeps decreasing. This started just today.

No matter how much free space I create by deleting some of the files, the space keeps going down..! I also noticed a couple of folders missing. There are no downloads currently.

I'm using a Dell XPS 8770 desktop that's running Windows 7 x64.. The system is currently running MalwareBytes Anti-Malware's "Full System Scan" for possible viruses.

Would appreciate any help. Thanks for your time.
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web_trackerComputer Service TechnicianCommented:
It could be the drive is failing rapidly, and more sectors as bad and inaccessible. This could be why all of sudden a folder is missing.  I would run check disk or maybe run a harddrive diagnositics on the drive.
Data Lifeguard Diagnostics is the western digital hard drive testing tool.

If the drive is failing backup your data immediately before it totally fails.
noxchoGlobal Support CoordinatorCommented:
Failong drive is out of question cause he gets the space back by deleting some data, or do I understand the statement of asker wrong?
If you did not format the drive after the purchase then it could have backup software on it which makes copies of already existing files.
web_trackerComputer Service TechnicianCommented:
he states that even though he is deleting files the free space on the drive is still decreasing. There has to be something going on with the drive if the free space is decreasing even though you delete files off the drive.
focus15Author Commented:
Thanks guys..

web_tracker is right.  The space comes back to 0 even after I delete files..

I ran WD Diagnostics Tool's "Quick Test" and this is what I got:

Test Option: QUICK TEST
Model Number: WD Ext HDD 1021
Firmware Number: 2021
Capacity: 2000.40 GB
Test Result: PASS
Test Time: 21:21:35, July 24, 2014

I have a new drive that I'm gonna install and copy the files asap..

EDIT: After a deleted a few files that came up after Malwarebytes' scan and the "Quick Test" above, the available space appears to stay constant and doesn't immediately go down to 0..

I'll keep checking and post back. Thanks again guys..
focus15Author Commented:
EDIT: After I deleted a few files that came up after Malwarebytes' scan and the "Quick Test" above, the available space appears to stay constant and doesn't immediately go down to 0..

I'll keep checking and post back. Thanks again guys..
noxchoGlobal Support CoordinatorCommented:
So your drive is ok and it was caused by some viral software on the drive?
check also what you are putting on the drive -  some backups can cause it when running dayly, or restore points
Davy ParidaensCommented:
Use Treesize it takes some time to index (grab a coffee) you will get a nice list:
Gerald ConnollyCommented:
use something like windirstat ( ) to visualise what using all the space.

Your original problem sounds like it could be a log file (or files)

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focus15Author Commented:
Thanks again everyone..

Like you guys suggested, I tried to check some unusual activity using "FolderSizes" and sure enough, I found this:

I was trying to download a video from YouTube yesterday and Internet Download Manager has created this log file for a whopping 141 GB..  You were right on the money, Gerald!

Also found out why that particular folder that was inside "DwnlData" (IDM's temp download directory) was deleted.

It looks like IDM considers anything inside its folder is just temp/unwanted files so it deleted my junk folder there...

I'm very happy now.. :) Thanks again for all the help!
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