Run Disk Cleanup, select the category and press "View Files"
To view the TEMP folder contents when the "View Files" button is unavailable. you can open an explorer window and type %temp%. This will open the TEMP folder ("%Temp%" is global ENV:VAR).
Everything in that TEMP folder is and should be temporary and can
be deleted. Unless an app that you used was programmed wrong or a
malicious app downloaded some large files into that folder. If you
see an app running from the TEMP folder it is more than likely malicious.
ADDITION (by Pyscogeek): Or you have just installed something or done
updates and have not yet re-booted the system. You should reboot before delete.
Disk Cleanup does not delete user files.
It does delete the following:
- Compression of old files
- Temporary Internet files
- Temporary Windows files
- Downloaded program files
- Recycle Bin
- Removal of unused applications or optional Windows components
- Setup log files
- Off-line files
System Files
- Previous Windows installations
- Windows Defender files
- Windows Update files
- Windows upgrade
This is not a complete list.
The Windows 7 Disk Cleanup tool states, "You can safely delete temporary files that have not been modified in over a week" - so I would assume this rule is followed when allowing the Disk Cleanup tool to perform the task. – MrWhite – 2018-01-12T13:19:07.743