Five Must Have Freeware Applications, if you are a windows user

1) Sysinternals Suit
A bag full of helpful utilities. Often when you feel, the inbuilt widows utilities are incapable of handling basic monitoring and troubleshooting requirements, you oughta try this one. Bundled with almost every type of monitoring tool (networking + system basics), these small apps are big in terms of how they work. The most handy of them is the ProcExp, an extension of the windows vulnerable TaskManager.

I often use TcpView and WinObj to get a hold on my network and system. Use it on your risk as these utilities override every firewall and windows settings. So, don't use it until and unless you are very sure about the operation.

The suit contains following utilities :
ProcMon (see which process is doing what)
ProceXp (an advance task manager)
TcpView (View your TCP Queue)
Autoruns (See whats running automatically on system startup)
RootkitRevealer (an advanced rootkit detection utility)
and many more
Download it from Microsoft Technet (size 10.3Mb):

2) Unlocker
This handy and small application provides a solution to popular Windows error messages like :
Cannot delete folder: its been used by another person or program
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.

Install unlocker and it will automatically embed itself into the right-click context menu. Then just simply right click the file which you are not able to delete and choose unlocker.

It will show which process is locking it. Select it, than select the operation and that's all your done! The most annoying process is explorer.exe, beware of it. Terminating it might make the system unstable but here is a quick trick. Go to taskmanager>run and type explorer.exe. The process will be restarted.
Download it from here(255Kb) :

3)CCleaner

Windows saves a lot of temporary files without your consent and it generally takes a lot of useful system space (in Gbs).CCleaner is a brilliant system optimization, privacy and cleaning tool. It removes unused and temp files from your system making Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. Additionally it contains a fully featured registry cleaner, an application uninstaller and startup manager.

download it from here (3.14Mb)

4)WinRar
Contrary to popular Windows compression tool winzip, winrar provides advance compression and archiving techniques. It can backup your data and reduce the size of email attachments, decompress RAR, ZIP and other files downloaded from Internet and create new archives in RAR and ZIP file format.You can also split files if they are bigger in size and later on winrar will automatically combine it as it was previously.
I have tested it's compression technique on many file formats like avi, txt, mp3 etc and its way better than WinZip's technique.
Download it here (1.31Mb)

5)Microsoft PowerToys for Windows XP

PowerToys are additional programs that developers work on after a product has been released. In other words, the left out inbuilt applications which Microsoft thought might come in handy. And they are amazingly handy indeed! A total of 15 utilities which are capable of performing some quick and useful operations.

Color Control Panel Applet : this tool helps you manage Windows color settings in one place.

SyncToy: can help you copy, move, and synchronize different directories from different sources.

RAW Image Thumbnailer and Viewer : provides thumbnails, previews, printing, and metadata display for RAW images.

ClearType Tuner: It lets you use ClearType technology to make it easier to read text on your screen, and installs in the Control Panel for easy access, making it a must have application.

HTML Slide Show Wizard: This wizard helps you create an HTML slide show of your digital pictures, ready to place on your Web site.

Open Command Window Here: This PowerToy adds an "Open Command Window Here" context menu option on file system folders, giving you a quick way to open a command window (cmd.exe) pointing at the selected folder.

Alt-Tab Replacement: With this PowerToy, in addition to seeing the icon of the application window you are switching to, you will also see a preview of the page. This helps particularly when multiple sessions of an application are open.

Tweak UI: Definitely the most important powertoy which gives you access to system settings that are not exposed in the Windows XP default user interface, including mouse settings, Explorer settings, taskbar settings, and more.

Power Calculator: With this PowerToy you can graph and evaluate functions as well as perform many different types of conversions.

Image Resizer: This PowerToy enables you to resize one or many image files with a right-click.

CD Slide Show Generator: With this PowerToy you can view images burned to a CD as a slide show.

Desktop Manager: Manage up to four desktops from the Windows taskbar with this
PowerToy.

Taskbar Magnifier: Use this PowerToy to magnify part of the screen from the taskbar.Webcam

Timershot: This PowerToy lets you take pictures at specified time intervals from a Webcam connected to your computer and save them to a location that you designate. Source:

Microsoft.com
Read and download them from here