If I posted all the awesome free software within this tread, then I would fill up whatever server this website resides in, causing it to... implode!
Here's a few of my faves:
Notepad
Paint
Windows Task Manager
Windows Live Messenger
Alright alright... here's a proper list:
AIDS II
Ah
Acid
5lo
Bomber
Eliza
...and that's just to name a few! (it's a joke... they're viruses, don't download them xD)
OK, an absolutely not a joke list:
TweakUI - Excellent for making most basic to intermediate tweaks to Windows 95-7 with absolute ease.
uTorrent - A very popular P2P download problem, which is very good, IMHO.
Windows Live Essentials - I know this is fairly boring and standard, but it's free, and so damn good!
ooVoo/Skype - Both great in their own right, even though I still prefer Windows Live Messenger.
WinRAR/WinZip - Although not truly free, their trials are very, very good, and I remember using them as far back as the 90s.
SMPlayer - Absolutely sensational program for all video media types, with several features, a great UI, performance, and compatibility, this program is an absolute must for those who constantly access video files.
MSI Kombuster - Very useful for benchmarking your GPU, and hey, it's free.
Smart Defrag 2 - Very good defragmentation program, with some nice features and it does the job very well, in my experience, as well as others I have know to use it.
ZoneAlarm - This is the ultimate free antivirus/firewall suite you will ever need, as far as I'm concerned. Nothing beats it, IMO. Although I have had to tweak it a lil, it does now work perfectly for me, and I'm sure would for MANY others. It's amazing!
I would list more, but I CBA to look through loads of my backed up software going back some years.
Good luck with your 'wares!