Everyone loves a good mystery--but neither your PC's inner workings nor your daily schedule should keep you guessing. This month, I checked out a Task Manager supplement, a click-saving Firefox extension, and a versatile calendar. All of them can be had for free.

Safer System Spelunking

Windows' Task Manager is like a boring professor: very little information and too much jargon. In contrast, the free SystemExplorer is like Indiana Jones taking you on a field trip, guiding you through your PC's activities in dizzying breadth and exquisite detail.

SystemExplorer tells you the file path, the software responsible for the application or process, its publisher, and a description. SystemExplorer is free--but if you like it, PayPal a few bucks to the volunteer developers at Mister Group.

What Lurks Behind That Link?

Whether they lead to files or to Web pages, links look the same. Click unwarily, and you could download a slew of unwanted PDFs--or worse. Link Alert, a free extension for the Firefox Web browser, lets you know instantly what kind of file lies behind a link.

Link Alert, from an author known only as Con­lan, installs directly into your Firefox browser. You may forget that it's there, at first; when you mouse over a typical Web page link, nothing happens. But when you mouse over a link that goes to any of the 12 supported file categories (which include Adobe PDF, JavaScript, Microsoft Word, and .zip), an icon appears: a musical note for audio files, a filmstrip for video, a gear for applications, and so forth.

Armed with Link Alert's information, you'll save yourself unnecessary clicks and keep your PC clean.

Bring On the Rainlendar

Most full-featured desktop calendars are clunky space hogs, and many smaller ones lack useful capabilities. Rainlendar Lite strikes a balance, offering plenty of ways to manage your schedule in a small, easy-to-use, and free package.

Rainlendar Lite has the essentials: alarms, prioritizing, easy scheduling of recurring events, and a search tool. But its main claim to fame is its customization features. You can choose components such as Events, To-Do, and a monthly calendar; arrange them to your liking; and then dress them up with selections from the hundreds of free skins from Rainlendar.net. (For example, I changed the skin for the mouse-over Tooltips to make them less obvious.)

Rainlendar Lite's basics are intuitive, but if you delve into the options menu, you can create a calendar to fit the way you work--you'll never be surprised by a meeting or deadline again.

Developer Kimmo "Rainy" Pekkola offers Rainlendar Lite for free. The Pro version (15 euros, or about $24) adds Google and Outlook calendar support and networked calendar sharing.

Did you have an interesting experience with one of these programs? Is your favorite file missing from PC World's Downloads library? E-mail your comments to Laura Blackwell. Messages containing attached files will be deleted unread.