Over 380GB of temp files I can't find or delete

The screenshot is worth checking carefully: “409 GB / 794 GB used” appears to show overall drive usage, not necessarily 409 GB of temporary files. That row alone doesn’t establish that you have hundreds of gigabytes of disposable data.

1. Click the arrow beside Temporary files and let the scan finish. Check the individual categories and their sizes. If they don’t add up to anything close to 380 GB, don’t keep deleting folders to chase that number. Also leave Downloads unchecked unless you intend to delete its contents.
2. Open This PC, right-click the affected drive, and choose Properties. Compare its used space with the figure in Settings. If it matches, the number you’re seeing likely refers to the whole drive.
3. If the detailed Temporary files page really does report 380 GB but offers no corresponding files to remove, use a disk-space analyser such as TreeSize Free, run as administrator, to locate the large folders. Use it to inspect first, not to delete unfamiliar system folders.

Large games can account for hundreds of gigabytes of normal installed data. If the space is in a game library, manage it through the game launcher. If Settings reports a huge temporary-file total that doesn’t match the actual folders, a stale or incorrect storage classification is possible—it isn’t a reason to manually clear Windows system directories.