Today's GOTD adds Microsoft C/C++ runtimes, installs a service, and records more installation data than many apps, meaning that you get 815 new registry entries. Installing the app means you get the program's folder, plus folders in My Documents & Public Documents, and an .ini file is added to C:\Windows. The C/C++ runtimes account for many of the new registry entries, and adds just over 40 new files. Registration seems to record a disk ID, so double check activation if you move the app. The portable option in the setup dialog requires that you have an USB stick connected, and adds several registry entries during install -- afterwards using the portable version on a different copy of Windows gets one new registry key. The app by default uses the Public Documents folder for storage -- you can change that in the software's options to the USB stick, but that may or may not stick when the USB stick is inserted into another PC using different drive letters. The portable version includes the setup file for the C/C++ runtimes, but it was not executed -- it *may* execute & install those files if they're not present, but I can't confirm that. And the portable version does not include the service to run cleanup in the background automatically.
abylon SHREDDER Private is a combination of a cleanup app, without a registry cleaner, plus a file shredder & duplicate finder. If you don't have software for file shredding & cleanup already, it's worth considering / trying today's GOTD, especially in the US where there's nothing like the EU's GPDR. As far as what's recoverable from a copy of Windows, you can research digital forensics, but a general rule of thumb if you Really want to protect your privacy, is to consider your PC like the internet -- data stored there can seem to be immortal.
Practically speaking, by the time someone gets their hands on your PC/laptop you're already in for some trouble. They've already committed themselves to the idea that you're guilty, e.g., getting a warrant -- now they're out to prove it. And those doing the searching may not be all that qualified, or honest -- they may or may not be corrupt, but they don't want to get in trouble with their boss for saying you're guilty [when you aren't] either. And they could have amassed all sorts of inaccurate or mistaken data beforehand. Data collection is a bit of a nightmare in the US, with companies like Meta & T-Mobile and all sorts of federal, local, and state agencies eager to sell their databases to whomever will pay. You also have companies that collect all kinds of privacy violating data, sometimes illegally, so they can sell it to whomever. Buyers include federal agencies like ICE [who won't say why], along with local & state law enforcement. Microsoft stopped selling their facial recognition software, because people in law enforcement didn't bother to actually look at the matches to see if they were in fact matches, and those same people are just as likely to ignore mismatches in any other data they collect. IOW be CAREFUL.
[For women in some states it's gotten or is about to get worse, with overzealous prosecutors anxious to rack up convictions they hope will get them votes in upcoming elections.]
Cleaning up left over garbage is also good from a maintenance standpoint [if nothing else reducing the size of backup archives], as well as helping to preserve privacy, while accumulating junk just bothers some of us, e.g., you might have thousands of .tmp files in a relatively obscure Windows folder -- check the location if you want, & maybe run this command in PowerShell to delete them all: Remove-Item C:\Windows\System32\config\systemprofile\AppData\Local\tw*.tmp
File Shredders are based on how a conventional Windows hard disk works. Files are stored in small chunks, with a sort of master TOC listing their location, what chunks make up what files, and in what order. Permanently deleting a file means it's removed from that TOC -- that's it. Since the file system now lists storage spaces with deleted files as free space, they can be overwritten, but how soon that will happen is random. But free space can be zeroed out [I use Precompact from Microsoft on my VMs prior to compacting the VHDs], so why shred?
Well, a conventional hard disk uses read/write heads that float on a cushion of air over the platters storing data, and they have a little bit of wiggle room. If those heads are all the way to the right when data's written, and all the way to the left when it's overwritten, a tech with the proper equipment might be able to read traces of the original data that wasn't covered up when that storage was written to a 2nd time. So a file shredder overwrites that storage space several times, because odds are at least one of those times the read/write heads will be in the same position as when the original data was written. A 2nd feature offered by abylon SHREDDER Private, but not all file shredders, is the ability to shred what the app's product page refers to as *cluster tips*. Data is stored in small chunks that are a fixed size. Sometimes at the end of a file there isn't enough data left to completely fill up a chunk or cluster. In that case the rest of that chunk could still hold data from an earlier file.
SSDs are much more complicated. They try to spread the writing of data around so that each bit of storage receives the same amount of use [wear leveling], and have extra storage to replace any small portions that might become defective. They also have different schemes where data isn't written continuously, as with a regular hard disk, but for example always as a full page that can include existing data. They normally do have TRIM, which proactively clears storage with deleted files -- overwriting involves two steps, clear then write, so clearing ahead of time makes them faster. But the long and short of it is stray bits of data can persist. Because of that they often have a built in command that returns the SSD to it's original, out-of-box state, BUT, depending on make & model, it may not work 100%.
That all said, Windows registry holds far more tracking data than most would imagine. nirsoft[.]net has a huge collection of free tools you can use to get a better idea of the kinds of data stored, and if you wanted, you could also use them to maybe check to see if abylon SHREDDER Private did its job. All this doesn't begin to address the personal data gathered when you go online. A VPN will hide your IP address and prevent monitoring traffic & destinations, though depending on the VPN service, all that may be logged. The TOR browser routes your traffic through several anonymous proxies. Using a browser in private mode prevents history & cache storage. Linux does not have Windows registry, & there are distros focused on privacy. Personally I prefer using a VM. That copy of Windows is stored in a single file [a .vdi using VirtualBox] which can be copied & stored elsewhere -- after I use that VM I can copy that saved .vdi file over the top of the one I just used, returning everything to it's earlier blank state. And VirtualBox lets you use random MAC addresses, which can be recorded when you go online & are normally unique to your PC.