Countdown timers with audio alert and popup reminder - Windows Freeware. This program lets you set up a number of countdown timers, with an audio alert and a popup window when the countdown reaches zero.

Timers are specified in days/hours/minutes/seconds, and if you close the program with active timers it will automatically restart them with the correct remaining time when you reopen it. Free software from the author of the Hal Spacejock series.