Kind of a long URL -- Sorry -- but concerned that because the link I got in an Ashampoo email included info from that email, it might be limited to one or two downloads. Instead I found an affiliate link.

ashampoo[.]com/frontend/registration/php/trial_step1.php?edition_id=l9j8afkizqag4np6yv6dyffr8ykph3rs&wgu=11173_116019_15963265185574_955121d9d5&wgexpiry=1604102518&utm_source=webgains&utm_medium=affiliate&utm_campaign=affiliate_webgains&utm_content=webgBundle&siteid=116019&session_langid=2

Basically it's a pretty light app, probably part of one of their optimizers, with a really simple GUI, the ability to select everything to be deleted, or not, and automatic backups [though you should still backup Windows anyway, since if it won't start, you can't count on this registry cleaner restoring one of those backups]. Most of the app is in its program folder, taking up about 20 MB with 349 files -- deleting the unneeded language & uninstall files brought it down to 14.5 MB with 163 files. There doesn't appear to be a difference installing in 32-bit vs 64-bit Windows other than the registry entries added... in 32-bit Windows you get an Ashampoo key in HKLM\ Software, while in 64-bit Windows you get one key in HKLM\ Software plus one key in HKLM\ Software\ WOW6432Node. You do need to register/activate the app with an Ashampoo account -- to save a few seconds adding the app to additional copies of Windows, that 2nd key includes the registration/activation info. An image of the [imaginary] software box is added to Users\ [UserName]\ AppData\ Local\ Ashampoo\.

Windows registry includes all sorts of info [or BS if you prefer], including links or pointers to other registry entries &/or files. Like every other registry cleaner Ashampoo Registry Cleaner 2 looks for links where the target is missing. A more detail oriented approach would be to use Regedit to check out the broken links it finds, because you *might* be able to get rid of an entire key with sub-keys, rather than the single line entry listed in the app. If that's too much hassle, then you can just let it do its thing.

The main way you can get into trouble is because some programmers are idiots, and because some software is built upon years [sometimes decades] of old code that no one ever looks at. So, you can wind up with links in the registry that don't point to anything, but the software checks for those entries anyway, and if they're missing, it'll misbehave. FWIW, I think that's also how registry cleaners fix some problems, breaking software that's already misbehaving unbeknownst to the user.

That all said, it's entirely possible to use a registry cleaner and not experience a single problem -- millions do. It's also of course possible to break something, as above. Will cleaning the registry help? Sometimes -- it depends. There are people that'll swear Windows never needs it, that the size of the registry and the entries in it are irrelevant, and if you want to join them in drinking that Kool-Aid, enjoy. I'll just point to all the bugs surfacing in the latest version of Win10, After An Extra 5 Months Of Testing! When you see the word Microsoft, there's a huge difference between what's promised, what should be, and reality. Some people say it helps, while others don't notice a change, but then some people install and try an awful lot more software than others. Some people are picky on what software they'll install -- some clearly are not. Some devices have plenty of horsepower & RAM, so they can read a huge registry without a hiccup -- many devices don't have that horsepower or memory and so may choke a little.