In order to use digimodes like WSPR or JT-like modes you need an accurate computer time. Dimension 4 is an easy way to synchronize your computer's clock if you're running a Windows-based operating system. I have succesfully used it on PC's with Windows XP and 8. Once Dimension 4 is installed, you can be sure that your computer works with the correct time.
Download the program for free here: