1. CCleaner
CCleaner is the best free registry cleaner program I've tested. It's easy to use, prompts you to backup the registry before it makes changes, and includes a number of other useful tools.
The CCleaner registry cleaner work on Windows 8 & 8.1, 7, Vista, XP, Server 2008/2003, and older Windows versions like 2000, NT, ME and 98. 64-bit Windows versions are also supported.
Piriform provides both installable and portable versions of their free registry cleaner.
2. JetClean
JetClean, a free registry cleaner by BlueSprig, isn't one I see mentioned a lot but I found it to be very well done.
The JetClean registry cleaner supports both 32-bit and 64-bit versions of Windows 8, Windows 7, Windows Vista, Windows XP, and Windows 2000.
JetClean scanned the entire registry in just a few seconds and has a well designed interface.
3. Wise Registry Cleaner
Wise Registry Cleaner comes in very close to the other top rated registry fix tools. They've put together a fantastic free registry cleaner program.
Wise Registry Cleaner comes in both installable and portable versions and can be used on Windows 8, 7, Vista, and XP. 64-bit Windows versions are supported.
Some big pluses for Wise's free registry cleaner include fast registry scans, scheduled scans, and a clear separation between normal issues and those that are "unsafe,".
4. Auslogics Registry Cleaner
Auslogics Registry Cleaner is another great registry cleaner program - it's probably one of the easiest registry cleaners to use out of all the tools I've tested.
Auslogics Registry Cleaner is compatible with Windows 8 and Windows 7 (64-bit and 32-bit), as well as 32-bit versions of Windows Vista and Windows XP.
If the several higher rated registry repair tools in my list don't give you the results you were looking for, give Auslogics Registry Cleaner a try.
Note: Before downloading Auslogics Registry Cleaner, you may be asked to download other programs, but it's easy to deselect them if you wish not to install them.
5. AML Free Registry Cleaner
AML Free Registry Cleaner wasn't part of this list when I first put it together which was an obvious oversight on my part. AML's free registry tool has been the most frequent reader-suggested addition to these programs.
The interface is a bit "old" in style, but AML Free Registry Cleaner makes up for that with a solid registry search, lots of still-free additional tools, and a long history of not accidentally causing more problems.
AML Free Registry Cleaner works on both 64-bit and 32-bit versions of Windows 8, 7, Vista, and XP, as well as on some Windows Server operating systems.
6. Registry Repair
Glarysoft's Registry Repair is another good freeware registry cleaner. Registry Repair is pretty simple to use and is a good option if some of the better tools aren't working out for you.
Registry Repair works in Windows 7, Vista, XP, Server 2003, and older Windows operating systems like Windows 2000, NT, ME and 98.
Note: After the installation of Registry Repair, you're asked if you'd like to run the program (this is typical) but you're also asked if you'd like to set "Glary Search" as your browser's homepage. Be sure to uncheck that if you're not interested.
7. SlimCleaner Free
Aside from a standard registry cleaning abilities, there are lots of completely free extras with this program like software update checks, startup optimization, system cleaning, and a lot more.
Advanced SystemCare Free works in Windows 8, 7, Vista, and XP, and 2000. A quick look at the program's version history shows that it's updated pretty frequently, which is great.
8. PowerTools Lite
PowerTools Lite 2013 is a freeware registry cleaner created by Macecraft, makers of several popular Windows utilities. PowerTools Lite was fast and found a similar number of needless registry entries as other tools in this area of my list.
PowerTools Lite 2013 works with Windows 8, 7, Vista, and XP.
Note: PowerTools Lite does ask for your email address but you can skip past it. If you do sign up, it's easy to unsubscribe the first time you get a message from them.
Kingsoft PC Doctor is another registry cleaner imbedded in a software suite.
This program is really easy to use, and the registry cleaner isn’t hidden away deep inside – it’s very easy to spot and run without any hassles.
Kingsoft PC Doctor is said to work with Windows 7, Vista, and XP.
10. EasyCleaner
EasyCleaner is one of the oldest and most trusted free registry cleaners out there. The interface is a bit dated but it's a solid registry repair tool.
The ToniArts website says that EasyCleaner works in Windows 7, Vista, XP, 2000, NT, ME, 98, and 95. Both installer and portable versions of this registry cleaner are available.
EasyCleaner took considerably longer than other registry cleaners to scan my registry but it did a fine job overall. I also liked how I wasn't asked to install a completely unrelated and useless browser toolbar during the install!