One note before all the free stuff, I learned something a few years ago. When it comes to antivirus and firewalls, the pay stuff will do what the free stuff comes short on, always.
Also antivirus =! firewall. Do yourself a favor and get some internet security suite. Yes the MS thing is good, but the pay stuff is still better. I'll take a couple seconds longer boot up for the sake of security any day of the week. Also eBay is your friend when trying to find the pay stuff for cheap (talking new here).
Now.......where do I start?
There are certain programs I don't like (Real Player, Acrobat, etc) but I don't like using a bunch of "alternatives" if I can do it with one program that just needs extensions or what have you.
K-Lite Mega and x64 (assign QT, Real, and Divx to WMP)
Foxit Reader (PDF)
DVD Videosoft does a lot but in a simple GUI. About to go pay though. (cd/dvd/media burner/ripper)
DVDFab Decryption/
DVDFab so I can play and/or backup DVDs and Blu-rays on my system.
RipBot264 for converting formats. It is a x64 program and (according to the .ini) is 10% then the x86 version. Again a simple GUI. Only converts to .MP4, .MKV, AVCHD, and DivxPlus. Keeps things simple by default but also can be more in depth for those who like to tweak. I love this program and it works very, very well. Only caveat (for those who care) is you need AVisynth, ffdshow (x86 and x64) haali, and java. Fwiw ffdshow and haali are used by K-Lite so with that you have two of the four already.
Zeuapp some might find helpful.
Hiren's BoodCD the save my.....well you know... CD. Name it, it has it plus a boot from cd mini XP and Linx. Life saver a few times already for myself and other people I know.
WD Acronis edition for nice backup, recover, OS img creation, etc for those with WD drives.
7-zip
For benching and monitoring, I'm just going to list. Copy, Google it and shouldn't be too hard to find them.
ATI CF Xtensions, Blue Screenview, Core Temp or Real Temp, CPU Tweaker (for cpus with on chip memory controllers), CPUz, CrystalDisk, GPUz (of course
), Hardware Info, HyperPI 0.99 (multi threaded SuperPI), MaxxPI, MemTest (in Windows), Open Hardware Monitor, wPrime, x264 Benchmark HD (v4.0 currently), and y-cruncher.
Sysinternals Suite (the only useful thing MS has made in a while)
edit: Oops almost forgot
Google Sketchup. Yea it's Google and I don't like how they install their browser (installs like a virus) but its a free CAD like program that is fun to mess with without being overly complicated.