Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Galarm - Social alarm clock and reminders
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows
Digital Clock 4 - Beautiful customizable clock with plugins