Note, if you're installing a few dozen apps, be prepared for it to take a while. E.g., (I checked 51 while testing for this article, the installs took over an hour.) And you need to keep an eye on the install, as a few items may pause, waiting for a click or two from you in order to continue. The 51 apps I installed take up about 1.6GB on the flash drive.
PortableApps.com isn't the only game in town; for example, there's WinPenPack (also free), with three default installs, one including tools and libraries for software developers.
Bootable operating system(s)
To diagnose/fix a machine so troubled it can't even boot from its own hard drive, it's helpful to have a bootable USB stick with you. This is primarily for system admins, tech support, and knowledgeable end users. One friend, for example, says, "I usually use it to reset Windows admin accounts and use various Unixy utilities on filesystems."
For Windows, "bootable USB" means "boot to an installer," to then load the OS onto a hard drive (or SSD), except for some versions of Windows 8 combined with a USB 3.0 flash drive. You will need a copy of Windows and/or its install disks, and a Windows license key.
For Linux distros, "bootable" can also mean a live-boot copy of the OS (like those bootable DOS floppies of yore). There's no shortage of ways to create bootable Linux USB sticks working from either Windows or Linux.
For example, LinuxLive USB Creator "creates portable, bootable and virtualized USB stick running Linux." Among its other virtues, by using a version of VirtualBox, LinuxLive "allows you to launch a LinuxLive directly in any Windows without any configuration nor software installation on your hard drive."
My colleague Tom Henderson advises, "When creating these USB install masters, if possible, start from an original disk or a known-to-be safe-download if possible, to avoid the danger of propagating malware or viruses, rather than creating them from what's on your computer."
Granted, not all target machines will boot from USB (older ones, in particular), or may need you to access and tweak BIOS settings.
In any case, be careful in creating these. Ideally, if you aren't already good at this, don't use your production machine, just in case something goes horribly awry.
System Boot/Rescue Collections
To test, diagnose, and fix/repair systems from a bootable Linux media, you'll want a bunch of apps. You can select and accumulate a bunch -- or get one of the bootable pre-fab distros, like SystemRescueCd or Ultimate Boot CD. Free downloads, affordable as flash drive or CD pre-loads.
Anti-malware/Anti-Virus and other security tools
For untrusted systems, it makes sense to carry some detection/removal tools. There's lots of free (and affordable) ones, like Malwarebytes, MyTurboPC, SpyBot Search And Destroy, and ClamWin. The "portable app collections" above include a handful of these.
If you're really suspicious of a computer, you'll probably want to start by booting from the USB drive and then scan the system's hard drive from apps also on the flash drive.
Passwords proliferate -- and while there are web/cloud-based apps to store them in, you might not be able to reach that online password stash. There are bunches of free password apps available, including PasswordSafe, KeePass, and Password Gorilla Portable. While I can't personally vouch for any of these, they're certainly worth a look to see if they meet your needs.
Sometimes you -- or a friend/family member -- forget the password to a machine's user or admin account or a donated or second-hand machine is locked. Happily, there are utilities -- many of them free, like OphCrack -- that let you recover or reset passwords.
Given that you may need to run the program on a computer you're unable to access, some of these tools include a bootable Linux distro suitable for a CD or flash drive.
(If you do go looking for a password tool, be careful where you get it from -- try SourceForge.net or Download.CNET.com.)
Aside from saving copies of any files you care about, one thing it's important to do before letting go of old computers and hard drives is to "wipe" -- scrub, erase, eradicate -- data so it can't be recovered. On Windows, simply doing a "Delete" and then "emptying" the Recycle Bin isn't good enough; you want to make sure those portions of the disk have been rewritten over.
And you may want to also do it to a disk on your computer, particularly to a notebook you carry with you -- keeping the programs and data you want, of course, but scrubbing deleted and draft files, along with cookies and other temp files you want to eliminate.
If you're prepared to wipe the whole disk, you can use Darik's Boot and Nuke (DBAN) (boot disk). If you only want to wipe selected files -- and possibly "free space" (which may still have old file fragments in them), you want a more selective tool, like Eraser (Windows utility, also available Eraser Portable), File Shredder, or Piriform's Ccleaner.
Cost: Freeware, Standard $24.95, Pro $199.95
PingPlotter is a good example of a niche-audience tool -- in this case, for monitoring and diagnosing network performance and connectivity graphically. It's also a good example of a tool you might have bought and therefore want to carry the non-free version of. (PingPlotter can be run from a USB drive.)
Portable browsers and email clients
Since "portable apps" work from and on their removable media, and don't leave data on the computer's disk, browsers and mail clients like these let you browse the web and read mail without caching login credentials, browsing history, etc.
Have USB flash drive, will travel
In addition to the aforementioned apps, there are, of course, hundreds (probably thousands or tens of thousands) of other programs worth toting around.
a backup tool
a default Cygwin install (setup.exe plus the standard packages), which is "a collection of tools which provide a Linux look and feel environment for Windows."
virtual machine(s) with all sorts of stuff
MP3 player and a day's worth of your tunes
any software needed to access your employer's network and systems. (VPN, secure browser, etc.)
What software do you carry -- or want -- on your keyring?
Daniel P. Dern is a freelance technology writer based in Newton Center, MA.