Windows Registries is a hierarchical structure where there are several keys and value. There 5 root keys called HIVES. These Hives are elementary for the operating system and shall not be deleted. Below given is picture containing hives.

This figures shows Root Keys or Hives of windows 2000, XP and windows 2003 operating system. All These five hives are important and have nodes under them which are called keys. Those Keys in turn also have keys under them. Key under the keys are called subkeys. Keys have VALUE associated with them which contains the actual data for a specific key. These VALUES can be of various types and contains Data within Them.

Below given is an Image of registry with details

Steps for creating a KEY

I will enumerate this these steps with an example, suppose have to create a new key called Test in HKEY_Local_machine\software.

1. Go to the root key hive, so go to Hkey_local_machine
2. go to parent key, click on the + sign and go to software
3. highlight the parent key by left clicking it once
4. Right click parent key, so right click Software key
5. In the context menu select new and then Key
6. This Will create a new key by the name NewKey #
7. Name of the key will be editable so edit the name to test and hit enter

Steps for creating a value

1. For creating a value you should know the Registry path of key for whose value is to be created
2. Following the same example we want to create a value called ValTest of Dword type.
3. Go to Hkey_local_machine and click on plus sign
4. then locate key called software
5. then click on + sign against software key and go to Test key.
6. Highlight test by left clicking it and the right click it generate context menu.
7. in that menu select new and then select Dword value.
8. This will create a new value on the right hand side of the registry pane.
9. name will be in editable format so edit the name to ValTest.

This will create a new value.

Differ Data Types and their use

REG_BINARY

Raw binary data. Most hardware component information is stored as binary data. It can be displayed in an easy-to-read format by using Windows 2000 Diagnostics. REG_BINARY data can be displayed and entered in binary or hexadecimal format in a registry editor.

REG_DWORD

Data represented by a number that is 4 bytes (32 bits) long. Boolean (0 or 1) values and many entries for device drivers and services take this data type. REG_DWORD data can be displayed in binary, hexadecimal, or decimal format in a registry editor.

REG_DWORD_LITTLE_ENDIAN

Same as REG_DWORD. A 32-bit number in which the most significant byte is displayed as the leftmost or high-order byte. This is the most common format for storing numbers in computers running Windows 2000 and Windows  98.

REG_DWORD_BIG_ENDIAN

A 32-bit number in which the most significant byte is displayed as the rightmost or low-order byte. This is opposite of the order in which bytes are stored in the REG_DWORD and REG_DWORD_LITTLE_ENDIAN data types.

REG_EXPAND_SZ

A variable-length text string. REG_EXPAND_SZ data can include variables that are resolved when an application or service uses the data.

REG_LINK

Indicates a symbolic link between system or application data and a registry value. You can use Unicode characters in a REG_LINK entry.

REG_MULTI_SZ

Multiple text strings formatted as an array of null-terminated strings, and terminated by two null characters. Values that contain lists or multiple values in a form that people can read usually take this data type. The values in a REG_MULTI_SZ entry can be separated by spaces, commas or other marks.

REG_SZ

A fixed-length text string. Boolean ("True" or "False") values and other short text values usually have this data type.

REG_FULL_RESOURCE_DESCRIPTOR

A series of nested arrays designed to store a resource list for a hardware component or driver.