Windows Vista : Registry Tasks and Tools (part 4) - Export and Import Data with Registry Patches

5. Export and Import Data with Registry Patches

Typing in Registry data gets awfully tedious, particularly when the N key breaks on your keyboard. Thankfully, it's not the only way to add keys and values to the Registry.

A Registry patch is a plain-text file with the .reg filename extension that contains one or more Registry keys or values. Double-click on a .reg file, and Windows runs the Registry Editor, which "applies" the patch to the Registry, meaning that its contents are merged with the contents of the Registry.

Patch files are especially handy for backing up small portions of the Registry, distributing Registry settings to other PCs, and duplicating keys.

For example, say you spend an hour or so customizing the toolbars in a particular application used by many employees in your office. Since most programs store their toolbar settings in the Registry, you can use a Registry patch to not only back up the completed toolbar setup—and thus save an hour of reconfiguring should your PC subsequently burst into flames—but to quickly copy the toolbar to all the other PCs in your office.

Or, perhaps you've spent the last six months gradually customizing your file types , only to find that a newly installed application or a Windows upgrade erased all your hard work and reset all your context menus. All you need to do is to make a Registry patch containing all your saved file types, and then reapply it should the need arise.

5.1. Create a Registry patch

Clearly, there's not much to making Registry patches with the Registry Editor. But it gets a little more interesting when you modify them, or even create them from scratch to automate Registry changes.

5.2. Edit a Registry patch

Since a Registry patch is just a plain-text file, you can edit it with any decent plain-text editor, or lacking that, Notepad (notepad.exe). The contents of the Registry patch will look something like the text shown in Example 1.

Example 1. Contents of a Registry patch created from HKEY_CLASSES_ROOT \.txt

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\.txt]
@="txtfile"
"PerceivedType"="text"
"Content Type"="text/plain"

[HKEY_CLASSES_ROOT\.txt\ShellNew]
"ItemName"="@%SystemRoot%\\system32\\notepad.exe,-470"
"NullFile"=""

The first line, Windows Registry Editor Version 5.00, tells Windows that this file is a valid Registry patch; don't remove this line. The rest of the Registry patch is a series of key names and values.

The key names appear in brackets ([...]) and specify the full path of the key, thus indicating where the values that follow are to be stored. On each subsequent line until the next key section begins, the name of a value is given first (in quotation marks), followed by an equals sign, and then the data stored in the value (also in quotation marks). A value name of @ tells the Registry Editor to place the value data in the (Default) value (as shown in the fourth line of the example).

You can go ahead and make changes to anything in the Registry patch file as long as you keep the format intact. Of course, those changes won't take effect in the Registry until the Registry patch is merged back into the Registry, a process described in the next section.

So, why would you want to edit a Registry patch file? Modifying a large number of Registry values often turns out to be much easier with a text editor than with the Registry Editor, since you don't have to open—and then close—each individual value.

There's no requirement that the keys in a Registry patch file need to have lived next to one another in the Registry, or that they be in any particular order. This means you can combine several separate patch files into one, and use it to restore any number of keys in one step. All it takes is a little copy and paste between side-by-side Notepad windows. The only thing you need to do, besides making sure all the keys and values remain intact, is to remove any extraneous Windows Registry Editor Version 5.00 header lines.

If you're creating a Registry patch to be used on other PCs, make sure you fix any references to absolute pathnames before you distribute the file. If, for example, your patch file references D:\Windows\notepad.exe, it'll cause a problem on any PC where notepad.exe is located in C:\Windows\. The best solution is to use expandable string values,  along with the appropriate system variables, like this: %SystemRoot%\notepad.exe. Now, since expandable string values are stored like Binary values in Registry patch files, such an entry would look like this:

"Open"=hex(2):26,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,\
00,74,00,25,00,5c,00,6e,00,6f,00,74,00,65,00,70,00,61,00,64,00,2e,00,65,00,\
78,00,65,00,00,00

					  

Now, as you may've guessed, it's considerably easier to edit expandable string (and binary) values in the Registry Editor than in any text editor, so you'll probably want to make such corrections before you export the key to a patch file. If you need to add a binary or expandable string value to a Registry patch file you've already started editing, though, all you have to do is return to the Registry Editor, create a temporary key somewhere, and then create your new value. When you're done, just export the key to a new file, delete the key from the Registry, and then copy and paste the value to your other Registry patch file.

5.3. Delete keys and values from a Registry patch

Although the Registry Editor won't ever create a patch that deletes Registry keys or values, it's easy enough to make one by hand. To delete a key with a Registry Patch, place a minus sign before the key name, like this:

-[HKEY_CURRENT_USER\Control Panel\don't load]

This patch, when applied, deletes the specified key and all of its values, as well as any subkeys. To delete a single value from a key, place a minus sign after the equals sign, like this:

[HKEY_CURRENT_USER\Control Panel\don't load]
"desk.cpl"=-

Of course, these tricks only work if you have sufficient permission to delete those keys. 

5.4. Apply a Registry patch

To copy the stuff from a Registry patch file back into your Registry, you need to apply it. The easiest way is to double-click the file (it doesn't matter if the Registry Editor is running or not).

If you see a UAC prompt at this point, click Continue. Then answer Yes when asked whether you're sure you want to add the information in the .reg file to the Registry, and finally, click OK when you see the "Information in MyPatch.reg has been successfully entered into the Registry" message. (You can also apply a patch from within the Registry Editor: from the File menu, select Import, select the patch file to apply, and click OK.)

regedit /sc:\folder\mypatch.reg

If the Registry Editor is already open and one of the keys modified by a patch that was just applied is currently open, RegEdit should refresh the display automatically to reflect the changes. If it doesn't, press the F5 key or go to View → Refresh.

When you apply a Registry patch, you merge the keys and values stored in a patch file with those in the Registry. Any keys and values in the applied patch that don't already exist will be created. If a key or value already exists, only its contents will be changed. It's important to understand that if a key you're updating already contains one or more values, those values will be left intact if they're not explicitly modified or deleted by the patch.