1. Notepad2
A notepad on mild steroids, if I may. A lot of people (read: developers/programmers) prefer Notepad++, but that, I think is too powerful for a person like me. Notepad2 has color schemes per programming language (to read/understand the code), antialias zoom, and is HIGHLY customizable.
Alternative: Notepad++

2. Avafind
Perhaps this should be right on top of this list. Avafind caches the file names and not the contents. So if you know the name of the file you are looking for, all you do is hit Shift+Esc and start typing the name of the file. Search results are returned at runtime and is insanely fast. Indexing for a 500GB hard drive takes not more than 60 seconds. Newly created files are automatically indexed in the Scout Bot feature. VERY VERY impressive piece of software, but shame that the company shutdown a couple of years ago.

Alternative: Everything

3. Opera
Well, no description needed here. A LOT of people prefer FireFox saying that it is a very powerful browser. Agreed, but have you seen the bloat on it when you install the addons to make it powerful as they say it is? Opera is one COMPLETE browser. It does NOT need any additional addons to make it powerful. Bittorrent, download manager, themes, built-in plugins, RSS reader, email and chat client, etc. What else can you ask for ? One thing which impressed me the most is that with the newer major versions of Opera, the size of the installer shrinks!

Alternative: Firefox

4. Paint.NET
People who use MSPaint are either retarded or are just ignorant. Those who use a cracked version of Photoshop just to resize their pictures are even more retarded (Yes, I know a few). Paint.NET is seriously MSPaint on double the steriods. Very very powerful for a novice who edits images on the fly and does not care about installing/purchasing a copy of Adobe Photoshop.
Alternative: GIMP

5. CDBurnerXP
Those were the days when you bought a new CD/DVD Recorder and you got a copy of Nero Burning ROM v6 with it. Nero v7 was insanely huge (it had a 700MB installer, if my memory serves me right). Switched to CDBurnerXP 3-4 years back and I am stuck on it since. A confusing name (with the part with ‘XP’ in it), people wonder if it would run on a Windows 7 box (well, yes it does!)
Alternative: Can’t think of any as good as CDBurnerXP

6. 7-Zip
I still see a LOT of people at work and otherwise use the evaluation version of WinZIP v7 which probably died back in the early 2000s. A few use WinRAR and the intelligent lot use 7-zip. Insane compression ratios, can uncompress RAR, ZIP, gz, tar.gz, and a whole lot of archives. Best part is that it can read contents of an ISO file too!

Alternative: WinRAR? Maybe.

8. Foobar2000
A no-nonsense, light media player. Sweet 2MB memory footprint when playing minimized. Maxes out at about 8MB of RAM usage. The kinky Winamp v5 who wants to whip the llama’s ass is still a preferred choice among Windows Media Player and others. Foobar is highly customizable with skins, plugins and what not. Note that once you start with the eye-candy, you will be sacrificing the available RAM on your PC. I like it simple and light.

Alternative: Windows Media Player 11

9. Unlocker
Many a times, when people want to delete a couple of files, Windows throws a message on the person’s face saying ‘Cannot delete file: Access is denied’ and does not let him/her delete the file until he/she reboots the machine. Worry no more, Unlocker is here. Right click on the file, click Unlocker, Click on the ‘Unlock All’ button and you are good to delete the file.

Alternative: None since I started using this one.

10. Launchy
OSX folk have QuickSilver, Linux users have Gnome-Do. Windows users have an app somewhere in the middle of the awesomeness of launching applications. A quick (customizable) hotkey combination and start typing the name of the app you want to launch. Hit Enter and it pops open! No need of going to Start > Programs > Blah 2008 > Blah 2008 blah. Launchy is also customizable with plugins. You start typing a simple mathematical calculation and Launchy’s Calcy plugin shows you the result and asks you if you would like to launch the answer in Google. How awesome is THAT!?

Alternative: Not sure if Rocketdock falls in the same category as Launchy

This is my list of 10 must-have applications after a fresh PC format. This list does NOT include any Personal Antivirus/firewall application – You are free to choose whatever you are comfortable with.

Feel free to post in your comments below