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Thanks again to each of you for taking your time to look at this. 1. MTA, on an elevated command prompt, that command returns: BuildNumber=15063 Caption=Microsoft Windows 10 Pro Name=Microsoft Windows 10 Pro|C:\WINDOWS|\Device\Harddisk0\Partition3 Version=10.0.15063 2. Hazelnut, this Dell Precision tower 5810 was a custom job I ordered from Dell Business Services, mostly because I lack the skills to set up a RAID1 myself. I ordered it with Windows 10 Professional already installed; I can't think of any reason Dell would have first installed Windows 7. But I do suspect that this problem with CCleaner is caused by something that is loading on startup that is backwards compatible, maybe Dell Audio or one of the other zillion Dell apps that run all the components on this system, and its causing CCleaner to misidentify the OS. My C drive is named OS (C:) It just occurred to me that when I have a few minutes tomorrow I should next try turning off Windows 10 Program Compatibility Mode, uninstalling CCleaner with its uninstall tool, rebooting in safe mode, and reinstalling CCleaner in safe mode in the hopes that this would force it to install with the correct version of Windows. I will update this thread if that works. Thanks again to everyone who has taken their time to reply.

ccleaner screenshot.pdf Thanks so much for taking time to comment. Trium, that PDF is for the same Dell Precision 5810 tower I have; mine has a RAID1 so there are a few minor differences from the standard model. MTA, here is a gif and a pdf screenshot showing my Win10 build and the CCleaner version. Any suggestions for resolving this issue are much appreciated.

I run Windows 10 Pro, 64-bit, on an original installation by Dell on a new Precision 5810. I have repeatedly installed and uninstalled CCleaner 5.562.10 (free version), but it always installs as a Windows 7 64-bit version, and although the registry cleaner can read the registry errors, it cannot correct them. I would have no problem paying for the CCleaner Pro version if this would be certain to solve the incorrect-Windows-version / registry cleaner problem, but if it won't, I'd rather just find another program. I've always liked CCleaner, though, and would prefer it if anyone knows how to get it to correctly read that this is a Win 10 computer. (The only Win 7 compatible programs I run are Adobe CS 6 ones, and I have tried removing all Adobe files from the Windows 10 startup, then rebooting, then reinstalling CCleaner, but that didn't make any difference.) Any ideas?