Reinstalling Windows is always a hassle, but if you've lost a few product keys then it could become a real nightmare. Are they on a CD case, a manual, in an old email somewhere? You might not be able to get your system working properly again until you can track them down.
It doesn't have to be this way, though. If you install a product key finder now, then it will scan your PC, and report on any product keys it finds (expect the list to include Windows and Microsoft Office as a minimum, and often many more). Print out the report or save it to disc and you'll always have your keys to hand, should disaster strike - much more convenient.
Which is the best product key finder, then? Good question - there's a lot of competition - but we put 10 of the best free key finders to the test in an effort to find out. Keep reading to find out what we discovered.
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1. Belarc Advisor

Total keys supported: 100+
Supported products include: Windows, Office, CyberLink apps, VMware Workstation, Nero Burning ROM

Belarc Advisor
Free for personal use only, Belarc Advisor is a powerful system information tool which builds up a very detailed picture of your PC hardware and software. This is way more than we need, but you don't have to pay attention to that information if you don't want to - just click Software Licences and you'll find keys for Windows, Office, CyberLink applications, Norton Internet Security and more.
Score: 4/5

Free PC Audit 2.1

Total keys supported: 10+
Supported products include: Windows, Office

Free PC Audit
Run Free PC Audit and it'll immediately display a summary of your PC hardware, installed and running software. The program only managed to display the Windows and Office product keys on our test PC, but it could still be useful to see and save the full list of your other installed applications. The program doesn't require installation, making it convenient to use, and doesn't include annoying adware - rare amongst this type of tool.
Score: 3/5

KeyFinder Thing 3.1.6

Total keys supported: 90
Supported products include: Windows 7, Office 2010, Visual Studio 2005, Adobe CS2-CS5 products

KeyFinder Thing
KeyFinder Thing is a basic key finder tool. It's a little dated now - there's coverage for Microsoft Visual Studio, for instance, but only up to 2005 - so is really only useful as a basic product checker for Windows and a few old games. Even then, the program doesn't fully work with 64-bit systems, and it comes bundled with the AVG Security toolbar for extra irritation.
Score: 1.5/5

LicenseCrawler 1.9.255

Total keys supported: 200+
Supported products include: Windows, Microsoft Office, CyberLink applications

The free-for-personal-use LicenceCrawler takes a unusual approach to finding product keys, simply scanning the Registry and displaying likely-looking values. This can make for a complex report, sometimes including entries which aren't product keys at all, and an in-your-face nag screen is another irritation. The program can find a lot of keys, though, and these are easily saved to a text file for later reference.
Score: 3.5/5

Magical Jelly Bean Keyfinder 2.0.8

Total keys supported: 300
Supported products include: Windows, Office, Nero Burning Rom 5-7

Magical Jelly Bean Keyfinder
Like many of the competition, Magical Jelly Bean Keyfinder is a little out-of-date; it'll give you your Windows 7 and Office 2010 keys, but for instance couldn't display our Nero 11 key as it doesn't support anything later than Nero 7. Unusually, though, the program has an editable configuration file, so if you're willing to do some work then you may be able to add support for one or two extra keys yourself.
Score: 3/5

MSKeyViewer Plus 2.2.0

Total keys supported: 101
Supported products include: Windows, Microsoft Office, SQL Server 7/2008, WinZip 8-14

MSKeyViewer Plus
MSKeyViewer Plus 2.2.0 is a simple tool which is mainly useful for displaying a few key Microsoft product keys: Windows, Office 97-2010, and so on. There are a few others, but these are notably getting a little dated now (there's support for WinZip 8-14, for instance, but the current version is 16.5). Still, it's portable, easy to use, and will copy your keys to the clipboard with a click for easy saving in some other document.
Score: 3/5

Product Key Finder 2.2.3

Total keys supported: 200
Supported products include: Windows, Microsoft Office

Product Key Finder
Its attempts to install a browser toolbar didn't get Product Key Finder off to a good start. And the program's product support isn't exactly up-to-date, either: it managed to find the keys for Office 2010 and Windows 7 on our test PC, but that was all. It's extremely easy to use, and can save whatever it finds in a CSV file as a record, but that's not really good enough. You'll get better results elsewhere.
Score: 2/5

ProduKey 1.53

Total keys supported: 15
Supported products include: Windows, Microsoft Office, SQL Server 2000/2005, Exchange Server 2000/2003

ProduKey is a tiny product key finder which only supports a few Microsoft products: Windows, Microsoft Office (2000-2010), SQL Server (2000/2005) and Exchange Server (2000/2003). Fairly basic, then, but the lack of any annoying adware bundled with the program is a plus point. And it has some useful command-line options, which include the ability to display product keys for all the computers on your network from one location.
Score: 3.5/5

SIW Home 2011 (build 1029i)

Total keys supported: 150
Supported products include: Windows, Office, Visual Studio, CyberLink PowerDVD

SIW Home 2011
SIW Home is a free-for-personal-user system information tool. It's actually best at telling you everything there is to know about your PC hardware, but it's not bad at software, either (click Software > Licenses), providing 7 product keys on our test PC and supporting 150+ products overall. This free version can't export your licences as a report, but you can still copy them to the clipboard so they're easy enough to save.
Score: 4/5

Windows Product Key Finder Pro

Total keys supported: 10
Supported products include: Windows XP/ Vista/ 7/ Server 2003/ 2008, Office XP/ 2003/ 2007/ 2010

Windows Product Key Finder Pro
Care is required when installing Windows Product Key Finder Pro, as it tries to install no less than two browser toolbars. Once you've got through setup, though, the program proves a good basic key finder, able to locate product keys for both Windows (including Server 2003 and Server 2008) and Office XP/ 2003/ 2007/ 2010, and save and print them all with a click.
Score: 3/5


If you're looking for a simple product key finder, which will just report the keys for Windows and Microsoft Office, then just about any of our 10 will do the job. But our pick would probably be NirSoft's ProduKey. It's small and basic, but doesn't come bundled with annoying adware (a rarity in this area), and can collect keys from across your network.
If you'd like to try to record more product keys then we'd recommend either SIW Home 2011 or Belarc Advisor. Both are superb system information tools which can also record quite a few software licence details: they're powerful, yet easy to use.
But if you're just after finding the maximum number of product keys alone then an honourable mention has to go to LicenseCrawler. The program's report looks like a dump of your Registry, and really isn't for PC beginners. But if you're an experienced user then you'll find this finds and reports more product keys than any other free tool, and the report can easily be saved to a text file for quick reference when you're next reinstalling.