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Registry size?


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This is a question in two parts.

First, am I right that 'The registry' is a collection of these 5

files (with no extensions) in C:\WINDOWS\System32\config:

* default



* software

* system

Second, and more difficult, what sort of size is regarded as 'reasonable' for the registry in total?

I got around to running a program I have called NTRegopt today for first time in about 2 years, on my XP Home PC. Directly prior to that I'd used System Mechanic, which deleted 64 registry entries, and rebooted. At conclusion of NTRegopt, I got message that it had reduced size by 2% to 58,372,096 bytes. That still seems pretty enormous to me. So I decided to try cross-checking it some way. After some

reading/googling, I concluded the registry was made up of those files above. I used R-click>Properties to get their sizes:

* default 512 KB

* SAM 24 KB


* software 29.035 MB

* system 9.250 MB

Adding those, I get about 38.7 MB, which is nearly 20 MB smaller than

NTRegOpt reported. Can anyone explain this variance please? (I've emailed the author of NTRegOpt too.)


Terry, West Sussex, UK

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Thanks At0mic. The author of NTRegOpt responded very quickly, and I now understand that there are eleven files making up registry. For anyone else ending up here with a similar query, here are their names and locations (on my system).






\Documents and Settings\LocalService\ntuser.dat

\Documents and Settings\LocalService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat

\Documents and Settings\NetworkService\ntuser.dat

\Documents and Settings\NetworkService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat

\Documents and Settings\[user name]\ntuser.dat

\Documents and Settings\[user name]\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat

That squares off with the size of 58 MB.

Anyone have thoughts on the second question please, i.e. about the large size of that?


Terry, West Sussex, UK

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Well, you have to think about the fact that the entire registry is used to manage every single resource on the computer, from knowing where to find a specific file, to settings for a program, and so on and so forth.

Think of every single check mark box that's available to you (there are many more than the common ones we use daily), as well as all the hidden settings that we don't see directly (e.g Prefetch). Then add on top of that all the strings needed to locate icons and programs. All this stuff adds up in the end... after thinking about it, 58MB doesn't seem that bad to me.

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deXter: Thanks, I'll try RegSupreme. I also use Norton WinDoctor. And I'm assuming NTRegOpt removes unwanted stuff too, to reduce size, but I'm not sure.

At0mic: ntuser.dat was one of my 11. userdiff makes 12. Anyone know its purpose please? Author of NTRegOpt doesn't include it and (although he intends to look at it more closely) says that deleting it appears to have no impact!

BTW, I didn't get email notification of these new posts in my own thread. Where in this site's confusing hierarchy will I find the appropriate setting please?


Terry, West Sussex, UK

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deXter: Are you sure RegSupreme is reliable? I just tried a series of tests, deleting nothing, and doing nothing else on my PC. It gave very strange results. Doesn't inspire confidence!

#1 Aggressive: 1305 entries

#2 New scan, Normal: 2293 entries

Should be the reverse if anything, if I'm interpreting 'aggressive' in the usual sense.

#3 Restart, Normal: 1190 entries

So what about the 2293?

#4 New scan, Aggressive: 2446 entries.

Tool 272 secs, much longer than #2

#5 New scan, Aggressive: 2896 entries

Another 450 entries from nowhere! (Took 256 secs, i.e. faster).

#6 New scan, Aggressive: 3087 entries

More, and more, and more. I wonder if it would go up indefinitely?

#7 New scan, Normal: 3440 entries

As for #2, seems quite illogical. And the 'Help' says nothing about the definitions of Aggressive and Normal.

Anyone else use this tool please?


Terry, West Sussex, UK


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NTregOPT doesn't remove any registry entries. It only rebuilds, or rather, compacts the registry so that blank spaces in the registry are removed. This is extremly useful after you remove a large number of registry entries (after using a reg cleaner), so that you can have a smaller and more efficient registry.

As for the behaviour you observed, I dunno, its very strange indeed. Which version of RegSupreme are you using? Im using the Pro version, which was btw, released todaty itself (a bug fix)


Do try out this version and see if you are facing the same problem.


I too use Norton Windoctor btw, but unfortunately WinDoctor has a tendeny to fix the entries rather than remove them entirely, which I dont personally like- I always follow the principle that as long as stuff goes out from the Registry...

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Title bar says RegSupreme 1.3. It's the demo, 30 days trial.

Tried downloading that latest, but I'm getting:

"www.macecraft.com could not be found. Please check the name and try again."

Any other users able to reproduce inconsistent results like mine?


Terry, West Sussex, UK

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deXter: OK, I managed to install that latest version. So far the couple of tests I've done give similar bizarre results:

#1 Normal 139 secs 1158

No deletions; no other user activity, New scan:

#2 Normal 254 secs 2344

What do you/others get when you do similar tests?


Terry, West Sussex, UK

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C:\Documents and Settings\Poppy>wmic registry get currentsize, maximumsi

Please wait while WMIC is being installed.

Parsing Mof File: C:\WINDOWS\System32\wbem\Cli.mof(Phase Error - 3)

Compiler returned error 0x80070424

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