Unknown .bmp files were found on my external hard drive

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Thread Starter
Nov 15, 2017
While running a duplicate file finder on my external hard drive I found over 30,000 files which are .bmp. I do not know where they came from Many are "copies" of my photographs. Since I never use .bmp for saving my photos I have not been able to explain this. There are many more which are not my photos but things like web pages, etc.
Since the only way I can delete all of them is to click each one separately. I am just wondering if I do a search of that drive using .bmp and then get a list and can delete all. Is there ever any file that is .bmp that should not be deleted? Hoping that there isn't so I can just get rid of all of these in one swoop.
Thanks for any help you can provide.

Tech Support Guy System Info Utility version
OS Version: Microsoft Windows 10 Home, 64 bit
Processor: Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz, Intel64 Family 6 Model 78 Stepping 3
Processor Count: 4
RAM: 16204 Mb
Graphics Card: support.com Remote Driver
Hard Drives: C: 1838 GB (925 GB Free); D: 23 GB (2 GB Free); G: 3725 GB (1555 GB Free); J: 2794 GB (332 GB Free); K: 1862 GB (245 GB Free);
Motherboard: HP, 816D
Antivirus: Windows Defender, Disabled
Jul 17, 2003
To delete all at once -

In the "Type" column click "Type" that should bring the "bmp" files together if they aren't in folders.
Click on first "bmp"
Hold down "Shift" key and click on last "bmp".
All of them should be highlighted. Press "Delete" key
If unable to highlight all of them at once you can still use this method to delete a number of them in batches.

NOTE: Make sure the bmp files are the only ones highlighted. Any other files highlighted will also be deleted when you press "Delete"!

Last edited:
May 31, 2011
Question. Has that external drive ever been your main hard drive in the past? Like if you removed it as an internal and put it into and external case as extra storage. I ask because you will often see bmp files along with web pages, html files etc. that will be in your temp folder under internet files. Explorer will save bmp files as its default file type and often when you visit web pages with pictures it will save them to a temp folder as thumbnails so that if you go back to that page it doesn't have to reload them each time. That's why when explorer seems slow they tell you to empty your cache. Ccleaner will delete temporary files but it looks in the C drives temp folders not in external drives. The size of the files can be a clue. You say some of them are your pictures. If you upload photos to a photo site or web page even if your photo originally was a 3mb file it will often save them on your drive as thumbnails as small as 30-50kb as a size restriction of the photo upload site you use. 30,000 is a tremendous amount of files, ho w were you running the comparison? comparing your C drive to the external or just looking for copies on the external alone?


Trusted Advisor
Spam Fighter
Nov 16, 1999
Be very careful, as many programs use bmp files for some of the features of their program. These will be within the Program install folders.
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