XMLEditPro

XMLEditPro is a simple and intuitive XML editor. It features Multi-Document Editing, Drag-n-Drog between documents/nodes as well as Cut and Paste. XMLEditPro also offers integrated Internet Explorer document browsing and can optionally edit files via FTP.
Win 98/Me/2000/XP

XMLFox

XMLFox is a graphical XML editing and validation tool for creating valid, well-formed XML documents and/or XSD Schema. It includes an XML View, XML Tree, XML Grid, and XML Script modes for editing, as well as extensive find capabilities for text and XML data. Additional features include XML and Schema Validation, standard editing features, XSD Schema building and more.
Win NT4/2000/XP

Peters XML Editor

A XML editor with syntax highlighting and customizable source
view. You can add code-templates and auto complete. Ability to
add, edit and delete Elements,Attributes,Text, CDATA
sections,Comments,Processing Instruction Also has the ability to
duplicate nodes. The Listview shows value of node. Files can be
launched in IE for preview.
Win 95/98/Me/NT/2000/XP

XMLPad

This small yet powerful XML editor is based on the unique custom-developed XML parser engine designed in accordance with the published W3C standards by WMHelp.com.
It includes the following features:
Powerful XML and DTD editor with color syntax highlighting, element range navigation and context-dependent code-completing wizard
Editing the DTD and XML using the tree and properties views, synchronized with the regular editor navigation
Editing XML using state of the art Grid View and preview in the built-in browser window
On-demand and online validation for DTD schema and XML files against the underlying DTD schemas
Auto-formatting the document
Generation the DTD schema from XML file and sample XML file from the DTD
Opening URL files as well as validation against the external DTD schemas
Win 98/Me/NT/2000/XP

Cooktop XML Editor 2.5

Cooktop is an editor and development environment for XML, DTD, and XSLT documents
Cooktop is a Windows application
Best of all, it's free!
Win NT/2000/XP

XML Viewer

MindFusion's XML Viewer is a freeware program - a present to all our friends and partners. It is used to examine the contents of an XML file in an easy-to-use environment. In addition you can make modification to the XML as follows:
Insert new items
Delete existing items
Add properties to specified items
Delete properties to specified items
XML Viewer 3.0 offers you also drag-and-drop option to manipulate the files more easily. As you can see from the screenshot it is very user - friendly and intuitive in interface.
Win 2000/XP

Microsoft XML NotePad 2007

Microsoft XML NotePad 2007 assists developers in creating XML applications.
It allows authors to rapidly build and edit small sets of XML data as a test bed during the development of XML-based applications. With XML Notepad, you can create XML document prototypes quickly, easily, and in an iterative fashion, using familiar metaphors.

XML Notepad offers an intuitive and simple user interface that graphically represents the tree structure of XML data.
Working with the standard building blocks of XML (Elements, Attributes and Text), authors are able to create reproducible data structures that can be easily filled.
It also includes XMLDiff to visually compare the differences between 2 two XML files.
Win 98/Me/NT/2000/XP

XMLmind XML Editor

XMLmind XML Editor Standard Edition is a very powerful authoring tool which has all the features needed to edit a document conforming to a DTD, whether standard (DocBook, XHTML, etc) or custom.

XMLmind XML Editor allows to edit large, complex, modular, XML documents. It makes it easy mastering XML vocabularies such as DocBook or DITA.

Some Features
Validating XML editor. Supports DTD, W3C XML Schema, RELAX NG, Schematron schemas.
Schema-directed editing. This makes creating invalid documents almost impossible.
Automatically switches to lenient mode to make it easy fixing an invalid element. Automatically switches back to its strict, validating, normal editing mode, once the element is fixed.
Can be used to edit XML documents not constrained by a grammar. In such case, XMLmind XML Editor (XXE) is still very nice to use because it simulates a very loose, dynamically created/dynamically updated, DTD.
Supports XML catalogs.
Win 2000/XP

XML Copy Editor

A fast, no-frills XML editor with DTD/XML Schema/RELAX NG validation, XSLT, XPath, pretty-printing, syntax highlighting, folding, tag completion, lossless import/export of Microsoft Word documents and a highly configurable spelling and style check.

Features
DTD/XML Schema/RELAX NG validation
XSLT
XPath
Pretty-printing
Syntax highlighting
Folding
Tag completion
Tag locking
Tag-free editing
Spelling and style check
Built-in support for XHTML, XSL, DocBook and TEI
Lossless import and export of Microsoft Word documents (Windows only)
Win NT/2000/XP/2003
Mac

Aioob XML Editor 2

The FREE XML Editor.
Edit XSL, XML, XSD, XSLT and FO documents with ease. The Editor makes code writing and reading much clearer and readable than writing or reading code written by hand.
Win 95/98/Me/NT/2000/XP

XAmple - Java XML Editor

XAmple XML Editor project introduces a java Swing based XML editor that analyzes a given schema and then generates a document-specific graphical user interface. Unlike other XML editors, the XAmple XML editor GUI exposes not just a tree representation of the XML document but rather a logical combination of the XML document and respective XML Schema. The user interface of the XML editor is highly logical and intuitively comprehensible.
Win 95/98/Me/NT/2000/XP

Amaya

W3C's Amaya is a Web editor, i.e. a tool used to create and update documents directly on the Web. Browsing features are seamlessly integrated with the editing and remote access features in a uniform environment. This follows the original vision of the Web as a space for collaboration and not just a one-way publishing medium.
Amaya started as an HTML + CSS style sheets editor. Since that time it was extended to support XML and an increasing number of XML applications such as the XHTML family, MathML, and SVG. It allows all those vocabularies to be edited simultaneously in compound documents.
Win 98/NT/2000/XP
Mac
Linux
Visit site for Mac and Linux downloads

MoreMotion XML Editor

MoreMotion XML Editor (mmEd), developed for editing and verifying XML structured files used in MoreMotion projects, is an easy-to-use XML Editor for both beginners and professionals.
Using mmEd, you can edit XML files used in MoreMotion projects or elsewhere, as well as project and library files with an *.mm* extension.
Win 95/98/Me/NT/2000/XP

TemplateMaker

TemplateMaker is an advanced XML and XSL Editor. Clear and easy to use IDE.

Source, tree, data edit modes. All the usual editor capabilities (cut, copy, paste, undo, redo) plus allowing syntax highlighting.
Win 95/98/Me/NT/2000/XP/2003

XML Viewer - view and edit XML files

MindFusion's XML Viewer is used to examine the contents of an XML file in an easy-to-use environment. In addition you can make modification to the XML as follows:
Insert new items
Delete existing items
Add properties to specified items
Delete properties to specified items

XML Viewer 3.0 offers you also drag-and-drop option to manipulate the files more easily. As you can see from the screenshot it is very user - friendly and intuitive in interface.
Win 2000/XP