Disk cleanup integrity

I have windows 7 professional 64 bit and ran Windows disk clean-up to see how much disk space I could free up.
I was surprised that windows 7 reported that it could free up 326 GB of disk space by removing temporary files alone (not temporary internet files).
Exactly what doe disk clean-up consider to be temporary files and is there any possibility that performing this clean-up could introduce any problems or loss of meaningful data ?
The disk is a solid state 939 GB disk formatted with NTFS and currently has 640GB of used space.
I have made a restore point but I imagine restoration wouldn't reverse the disk clean-up ?
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Roger AlcindorAsked:
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JohnBusiness Consultant (Owner)Commented:
If you run Disk Cleanup and especially also Clean up System Files, it will remove temporary files, old files in Software Distribution, some cleanup in WinSxS, some cleanup in System Volume Information and old Windows installs (Windows 10)

If you have never cleaned up before, there could be a lot to clean up.  300 GB seems a lot unless you have on board backups running.

I run Disk Cleanup weekly and have done for years and never lost anything.  

However, back up first before proceeding.

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bbaoIT ConsultantCommented:
performing this clean-up could introduce any problems or loss of meaningful data ?

NO.

I imagine restoration wouldn't reverse the disk clean-up ?

CORRECT.
nobusCommented:
if a disk cleanup causes loss of data, i'm sure MS would have lots of mails and Phone calls....
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Qlemo"Batchelor", Developer and EE Topic AdvisorCommented:
You are safe to remove temporary data, unless you have stored important stuff in one of the TEMP locations (which would be strange) yourself. No software stores anything there which has to persist.
However, 326 GB sounds a real lot, and so I would look into the temp folders to see if anything obviously large is stored there. C:\temp, C:\Windows\temp and %temp% (user profile temporay folder) are candidate locations.
nobusCommented:
you can use windirstat to check what's taking the space : https://windirstat.net/
Roger AlcindorAuthor Commented:
I checked the temporary files folders and couldn't account for the large amount of space reported by disk Clean-up. I proceeded with the clean-up and only about 40 GB had been recovered.
This was the first time that I had used disk clean-up.
thanks for your comments.
JohnBusiness Consultant (Owner)Commented:
Thanks for the update and I was happy to help
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