The same situation occurred on my computer...MANY duplicate files, but some with different types, .dll, .sys, .congfig, .exe. They are all the same size and created on the same day. But there are A LOT. Do I go through every one? Which ones are safe to delete?
Which version of Windows are you using?
Those file extensions suggest to me that these are probably system files that Windows has updated. (Probably as part of the monthly 'Patch Tuesday', which was yesterday/today).
Especially as you say that there are a 'LOT' that suggests system files.
If it's Win 10 then they may have been left over from the last six-monthly version Update.
If this is the case then Windows should remove the old ones itself after a while.
This will take up to 30 days after a version update.
Windows keeps these old files for a month so that you have the option 'roll back' to the previous version if needed.
If you want to remove them more quickly then run 'Disk Cleanup' with the 'Clean up system files' selected. (to see if it removes them as 'Previous Windows Versions').
Another possibility is that these are are backup files that are stored on your disc in case you ever need to restore Windows at any time.
Most computer manufactures include these on on the hard disc these days, rather than providing a CD. (Most modern laptops/tablets don't even have a CD drive).
Thank you. I did have to recover my whole Windows OS several years ago and I have some older files from a recovered external hard drive. Bt this list is LONG, and I have messed up my computer multiple times because I know enough just to be dangerous. I don't want to delete something that is required to boot the OS. I am using Windows 10 64-bit with the Insider's build.
Ahh, the Insider build. (You will have Redstone 4 (Spring Creators Update) running).
TBH I'm not sure just how the insider programme handles previous Windows build files, I would imagine it is much more likely to save previous versions of the files to restore in case something goes wrong with the insider build.
Insiders also get a lot more 'mini-version' updates than stable version users. (They get new versions in bits over six months rather than all at once)
Insider builds are beta testing versions and so more prone to errors, so it would make sense that they keep more backups of old files.
As a general rule, unless you are seriously running out of disk space then I would leave system files alone (even duplicates).
I regard the Duplicate Finder of CCleaner as more of a tool for finding duplicate photos/videos/music/documents rather than system files.
Try running the Duplicate Finder with 'System Files' unchecked and seeing if it still finds all these files.
I still think your best bet here will be to use Windows own Disk Cleanup to 'Clean up System files'. Run it as Admin.
If it doesn't remove the duplicated files then that would indicate that Windows Insider considers them as necessary (or that they are not system files).
You are walking into danger with duplicates. Leave them alone and be done with it.
If you are worried about space run https://windirstat.net
Thank you both very much. I have this almost irresistible compulsion to mess with the file duplicates, but, as you both recommended, I'll just leave them alone. Whew! I'm glad I didn't do something that I would regret.