Freeware I ALWAYS install. You?I've rebuilt two Windows OS'es from scratch lately, and I thought I'd share my "holy crap I need to install" programs with you. (That and I'll have a reference page!) While some of these have "Pro" versions, you do not need to buy any of those. If you want to - or are able to support the independent developers - then do so. This list is extremely Windows-centric, and yes, I realize the irony in using an Ubuntu image to illustrate it. I have Xubuntu and Puppy running in Virtualbox right now, so back off. You may notice that some links point to "Last Freeware Version", a great resource in itself. Personally, I have a lot more tweaks and hacks running - I use Blackbox4Win as my shell, for example, and a customized Samurize config - but these are the ones I hand out to people who are regular users.
Kiero Personal Firewall (XP and earlier)
Zone Alarm (XP/Vista/7)
Avast (Free Antivirus)
The (free) registration that Avast asks for every six months has confused people before, so I keep that in mind when choosing which of these excellent programs to use.
Spybot Scan & Destroy
Install both. If you share the computer with your kids, install TeaTimer and the IE protection stuff from Spybot.
General cleaning of temp/excess files
2gb free backup. It's what I use. I've heard people say good things about Dropbox, but since I know this system, I like it. It is also cross platform (and can sync), so if you have a work Mac or *nix system, you're almost certainly covered.
I've had so many damn problems with non-standard drivers that it's not funny. Use this to back them up to a CD to avoid having to scour the web when you reinstall your OS.
Best defragger in my experience. Especially with Vista, but also XP.
Ever have a window offscreen and you can't grab it back? This helps. An absolute MUST for netbooks.
Uninstalls all of a program, including crap left in the registry. You want the free version.
K9 Web Protection
If you have kids and want a netnanny, I use this one, largely because it's so customizable from *my* end, so *I* choose what gets through and what doesn't. You can also allow temporary access.
I love the desktops at Simple Desktops.
What's your favorite freeware to put on a clean install?