What's The Truth On Resistry Scan?

Every one seems to be the same . They all find errors and none of them fix or do what they say. They scan you're computer and then say to fix this purchase the real application for $$$. Is there a legit registry repair that will fix missing files like the LAME _enc.dll or the .exe files that can stop  downloads from working ?

Registry cleaners got a bad rep when Microsoft first released one back in the 80's. It was famous for doing awful things. Third-party vendors answered the need, but they all suffer from the same limitation, which is that "cleaning" the registry is no straightforward task.

The registry is a general-purpose database that any application may use to stash persistent data. Because that information is meaningful only to the app that put it there, finding meaning - or lack of it - in that data can be difficult or impossible. Consequently, registry cleaners have to be very conservative lest they inadvertently blow away something important.

To make matters worse, the internet has been flooded in recent years with fake diagnostic and repair utilities, and with fake virus/spyware scanners. Never, ever run any system scan from the internet! 99.9% of them are total frauds and many will actually deposit viruses on your computer.

I'll second papa's recommendation for CCleaner. It's been around for a while. It's compatible with all versions of Windows from W95 to W7. Best of all, it lets you decide what to clean and what to leave alone, and gives you the option to preview changes before they are made.

EDIT:
Warning #1: like so many freebie downloads these days, CCleaner will install the dreaded Yahoo! Toolbar if you're not observant during its installation. Do not install the Yahoo! Toolbar.
Warning #2: by default, CCleaner is configured to wipe out some things you may wish to keep, such as crash dumps, log files, registry backups and useful cookies (such as the one that lets you log in to this forum automatically).

CCleaner is good, and I use it on client computers (as well as my own), but it doesn't always find everything. When it does, I donate to Piriform (the company that makes it), because it's a useful product, and donations keep them in business.

Another good tool is Glary Utilities. The free version will not only scan the Registry (and hard drive) for junk CCleaner doesn't find, but it also has an option to compact the Registry, and that's quite helpful. A smaller Registry loads faster, in general.

Unfortunately, both of these utilities are updated almost weekly, so be sure you're running the latest version before you scan.

And like Bitflipper said, never download a "free Registry cleaner" from a Web site. They're almost always (I'd say 99.999% of the time) virus- or malware-infested scams.