You'll want to keep a copy of Recuva handy for the inevitable panicked phone call from your accidental deleter. As with the other tools here, Recuva is completely free. There's even a portable version that you can run off of a thumb drive, so there's really no excuse to be caught unprepared when the inevitable occurs.
Spend any time supporting Windows PCs and you'll find yourself becoming an expert at FTP. That's because the File Transfer Protocol is the de facto way of distributing device driver updates and patches to Windows customers. And depending on the prevalence of specific makes and models, you'll likely begin to learn the directory structure of your primary vendor's FTP site like the back of your hand.
Fortunately, Windows users have access to one of the more powerful FTP clients available: FileZilla. Now in its third major generation, this capable if somewhat homely application makes transferring large quantities of files a snap. A capable queue management system helps keep the uploads and downloads humming along while a nearly endless selection of configuration options and protocol tweaks ensures that, whatever the situation, FileZilla will come through every time.
Microsoft loves the ISO image format. From trialware versions of its OS products to its latest Patch Tuesday security fix collections, Microsoft distributes more software in the ISO format than any other vendor. So it comes as somewhat of a shock to learn that, as of Windows 7, the company still hasn't integrated a basic ISO image mounting/drive-emulation capability into its core OS. Basically, if you want to use an ISO under Windows, you need to first burn it to a physical CD or DVD.
Fortunately, a variety of free third-party solutions fill this void. My personal favorite is Virtual CloneDrive, from Elaborate Bytes. Simple to use and highly compatible with all versions of Windows, VCD makes it easy to mount and access an ISO image. Just right-click the VCD tray icon, select Mount from the context menu, and point the ensuing file open dialog to the desired ISO file. The image then appears as a virtual CD-ROM drive in Explorer, allowing you to access its contents like a real disk.
Note: I used to be a Daemon Tools fan. However, recent versions have proven unstable under Windows 7 (I've traced several Blue Screens of Death to Daemon Tools' kernel mode components), and the developer's lackadaisical attitude toward supporting new Windows versions has turned me off from this once class-leading utility.
If you regularly need to mount and access ISO images, make sure you take along a copy of Virtual CloneDrive. It's easy to use, installs in seconds (no reboot required), and provides the capability that Windows should be providing but doesn't.