basically this site is about reshacking the whole system, including the programs installed by windows, but in my case not all parts of my windows are hacked. there are some windows programs that i deleted and replaced with other programs. why? because i can change only the resources with reshacker, or just simply the program is a crap, or simply i don't like it. in example; windows media player. or just there are far more better programs to use.
program and other replacements
msn messenger
tips: miranda, trillian, ... skinnable, customizable messengers.

windows media player
tips: winamp or foobar + media player classic.

internet explorer
tips: firefox, opera, ... skinnable, customizable browsers.

outlook express
tips: foxmail, popcorn, thunderbird, ...

tips: notepad 2, metapad, ...

cmd console
tips: console v1.5 - windows console window enhancement.

task manager
tips: daphne, process explorer ...

picture and fax viewer
tips: irfanview, xnview ...

visualstyles. requires uxtheme patcher.

left* taskpane
tips: findexer - * in case if you have bottom or top shellstyle panel you will have both panel.

or you can replace whatever you want:
calculator, magnifier, mspaint, regeditor, disk defragmenter, the shell: explorer ... and so on.

tip a: i recommend using small, portable apps, or programs that can be executed from anywhere, and requires no installation.

tip b: oldversion.com - "Because newer is not always better"
shell extensions
Windows Explorer can be extended to support non-default functionality by means of Windows Shell Extensions, which are COM objects that plug-in the extended functionality into Windows Explorer. - not replacements, but can enhance your system in some ways. and i thought it is worth to mention some of extensions.

contextbg - screenshot
It adds a background bitmap to (a) common rightclickmenu(s). usage: put the dll into a folder you want, then type into the run dialog; regsvr32 *yourfolder-path* contextbg.dll. in example: regsvr32 c:/programs/here/contextbg.dll

byblos - screenshot
It adds a small bitmap to (a) common rightclickmenu(s). usage: put the dll into a folder you want, then type into the run dialog; regsvr32 *yourfolder-path* byblos.dll. in example: regsvr32 c:/programs/here/byblos.dll

explorer breadcrumbs - screenshot
Rather than navigating step-by-step through your folder hierarchy -- view your folders quickly and go directly to any location with a single click. Explorer Breadcrumbs is an add-in for Windows Explorer which contains a contextual series of buttons that allows you to quickly see and navigate through the entire folder hierarchy without leaving the current window.

folder size - screenshot
Want your Explorer folders to show sizes of folders and files in the same column like this? Find out how!

Command Prompt Explorer Bar - screenshot
The Command Prompt Explorer Bar is a handy Windows Explorer add-on for power-users that frequently work with the command prompt. Besides the fact that the toolbar provides quick access to the command prompt from anywhere in Windows Explorer, it also adds several convenient features like custom script macros, keyboard-less operation and more. Command Prompt Explorer Bar can be quickly opened by using a keyboard hotkey or from the Explorer bar tool menu.

bxNewFolder - screenshot
Use a hotkey to create a folder within Windows Explorer!
bxNewFolder adds a "New Folder" button to the toolbar of Windows Explorer. It also provides a hotkey (F12) to create a new folder within the Explorer quickly.

mdaxelerator - screenshot
It enables to define shortcut key for creating new folder and make possible to change some other stuff.

open subfolder - screenshot
Open Subfolder is a contextual menu extension for Windows which adds the ability to open a folder located inside of the currently selected folder.

unlocker - screenshot
Ever had such an annoying message given by Windows? like:
-Cannot delete file: Access is denied.
-There has been a sharing violation.
-The source or destination file may be in use.
-The file is in use by another program or user.
-Make sure the disk is not full or write-protected and that the file is not currently in use. - Unlocker is the solution!

SubMenuPack - screenshot
This package installs a new sub-menu in the right-click (aka "context") menu that appears on the Desktop and folder backgrounds. The sub-menu gives you the ability to customize the sub-menu by adding any of your favorite programs, scripts, etc. to a menu for easy access. It includes a "Configumilator" utility for creating new command options in the sub-menu.

contextaware - screenshot
With ContextAware, you can create multi-level menus to be added to the folder background's context menu. and you decide which files. - see help file in the zip.

awxToolbar - screenshot
This is a Toolbar for the Windows Explorer. You can define your own toolbar functions via an XML file.

findexer - screenshot
FindeXer is another explorer addon, but this one adds a Mac Finder bar to explorer. Instead of treeview, you can customize which shortcuts you want easy access to. Just drag the folder to the bar and you can even customize the icon.

firmtools shellextension - screenshot
Install this tool and it will add three new options to your menu when you right click on a picture file: convert, print, and thumbnail preview.

new-ext - screenshot
New-ext extends Windows Explorer context menu with a number of commands that crete a directory based on a template you configure.

image resizer - screenshot
This PowerToy enables you to resize one or many image files with a right-click. ideal for resizing pictures for websites quickly. No need to open the picture with any image editor.

more shell extensions:
managing these extensions: shexview

mel's shells
shell extensions
MSFN forum: shell extensions
15 useful shell extension
Shell Extension Software
shell replacements
in windows, the shell is explorer.exe. it provides the System tray, the Taskbar, the Desktop, and the Start Menu. if you don't like explorer, you can replace it with alternate shells that providing a new look, and functions.

here are some alternate shells:
lite step
geo shell
emerge desktop
black box

there is an other way to shell replacements. it's called shell packs. shell packs usually replace / modify visualstyle, shellstyle, icons, bitmaps, and windows files. shell packs sometimes mimic another operation systems look, like vista, or macintosh.

here are some shell packs: