BOOT CAMP 568 (18/03/09) – The Windows Registry, part 1


In the past few months I’ve noticed an alarming increase in the number of emails from readers who have been conned in to buying useless Registry Cleaner programs that purport to fix a wide range of computer problems, improve performance and increase reliability. I have to say these programs are mostly snake oil; they rarely make any difference and sometimes do more harm than good. In some cases the errors reported by the ‘free trial’ versions of these programs, and there may be hundreds or even thousands of them, are not harmful or they are completely fictitious, created by the cleaner program. Needless to say the software offers to remove them, but only after you’ve purchased the full version of the program.


Part of the problem is the widespread lack of awareness about what the Windows Registry is and what it does. It doesn't help that I and other PC Agony Aunts and Uncles regularly warn of the dire consequences of tinkering with this large and important system file. The Registry has become steeped in mystery and endowed with almost magical powers so it's hardly surprising that unscrupulous software companies have recognised the gap in the market and jumped in to peddle programs that capitalise on PC users fears.


The general advice that the Registry is best avoided by absolute newcomers and wary novices still holds true but it’s nowhere near as scary as it sounds. In fact I would go so far as to encourage PC owners to have at least one quick glance at their PC’s Registry. Not that it’s very interesting to look at, but once you’ve seen it and understood a little about how it works I suspect that you will be less likely to be taken in by the scare and con merchants. Later, in this short series, if you are feeling brave, we’ll tweak a couple of settings, and look at ways to fiddle with the Registry without getting your hands dirty or endangering your machine and yes, if you really must, I’ll suggest a couple of free and safe Registry Cleaners. 


So let’s begin with the basics and the somewhat dull fact that the Windows Registry is just a big database. It is used to store settings and information about Windows, your PC’s hardware, the programs that you use and the computer user’s preferences and customisations. See what I mean? It’s already starting to sound less intimidating...


Of course there’s a bit more to it than that and the Registry is also responsible for a number of housekeeping tasks and behind the scenes operations but the point is, it is primarily a repository for the data that determines how your computer works, looks and behaves, everything from how long it takes before your favourite screensaver appears to how much memory is being used by running programs.


I said the Registry was big, and it is, but its size varies widely from one PC to another. Depending on the version of Windows that you are using, your software and how long you have been using your system, it can be anywhere from 30Mb to several hundred megabytes.


The Registry grows quickly as you customise Windows and install new programs and this can be a problem. Each new piece of software can create scores and sometimes hundreds of new Registry entries. In theory they should all be removed when the program is uninstalled. The trouble is not all programs clean up properly when they go so the Registry swells with redundant entries. They are mostly harmless but occasionally a new program, or a newer version of an application clashes with an old Registry entry and up pops a worrying error message.


The size of the Registry is also blamed for slow startup and shutdown and this definitely was the case in earlier versions of Windows, as we’ll see in a moment. However, from Windows XP onwards only the parts of the Registry that are actually needed are loaded during the boot up sequence and even if the files concerned have become bloated and unkempt it should only take a second or two to process so in most cases Registry cleaning and pruning software makes little or no difference to boot up time.


You may be wondering where the Registry is stored. In Windows 95, 98, SE and ME the entire Registry was contained in just two or three files, called System.dat, User.dat and Classes.dat (the latter appeared in Windows ME) and they all live in the Windows folder. Current versions of Windows (XP, 2000, Vista and Windows 7) are built on the Windows NT platform and partly to avoid problems of a slow boot up the Registry is split into multiple files stored in two locations. The bulk of the Registry files can be found the Windows\System32\config\ folder. The main files are called Default, SAM, Security, Software, System and UserDiff and they are concerned with global or system wide settings. A second set of files are stored in the Documents and Settings\<yourname> folder in XP (Users\<yourname> in Vista, called Ntuser.dat, there is one of these for every user and this stores all of the personal settings and customisations for each user. 


Next Week – The Windows Registry, part 2





Security Accounts Manager – encrypted database file used to store passwords



Facility in Windows ME, 2000, XP and Vista that stores and records changes to key system files, which can be used in the event of a crash or serious problem to restore Windows to a previous known good configuration



Windows New Technology; family of operating systems on which XP, Vista and Windows 7 is based, first released in 1993 and the first to use a 32-bit architecture



Windows does its best to protect the Registry and a pristine backup that is never updated is made automatically when Windows is installed (they have the extension .sav). If needed they could be used to reset Windows to day-one. Current Registry files are backed up by System Restore, which on most PCs occurs every 24 hours.


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© R. Maybury 2009, 2402


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