Good Business Article on "Tips for the Daylight Savings Headache"
Here's the key part of the article
If your PC is running the most recent version of Microsoft (MSFT) Windows, known as Vista, you don't need to do anything. The new operating system was programmed with the new time-change schedule in mind. Prior versions, however, need an update, which can be downloaded.
See Microsoft's Daylight Saving Time Help & Support Center for more information on versions of Windows going as far back as Windows 2000 Professional Service Pack 4. Versions of Windows that are even older, including Windows Me, Windows 98, Windows NT, and Windows 95, need a little more help. Your best bet is to use a utility called tzedit.exe, which can be found either on the Windows installation CD or downloaded from Microsoft's Web site.
If you're an Apple (AAPL) user, most Macs bought during the last two years and running Mac OS X should be fine, provided you've been regularly updating your software. Updates have already been issued for Mac OS X version 10.3 (Panther) and 10.4 (Tiger).
Not sure if you're appropriately updated? While connected to the Internet, pull down "Software Update" from the Apple menu. If they're needed, the required updates will install automatically. If your Mac runs any version of OS X prior to 10.3, you'll have to adjust the time settings manually. In "System Preferences" find the "Date and Time" icon, and deselect the option to automatically adjust for Daylight Savings Time. If your Mac runs Mac OS 9.2 or earlier, you'll have to find the "Date and Time" control panel and uncheck the option to change to Daylight Savings Time automatically. Then set the time yourself.