Moving licenses between computers is never a problem, and there's no charge if you stay in the same version (v2004, v2006, etc) you originally purchased.
Just uninstall the software from the original computer, then using the new machine, visit the download section of our website and grab what you need. If you haven't purchased a license for our current version (at the time of this writing, v2008), you can find older copies at at www.empirisoft.com/download_old.aspx.
After you finish the installation process, you'll need to send us an activation code which appears on your computer screen.
These codes are generally to sent to the sales department, whose email address is sales AT empirisoft.com.
Unfortunately, license codes are unique to each machine, so you can't just re-use the ones you have presently.
That's it!
Let us know if you get stuck.
Oh - and if you can tell us who originally purchased the software you're moving when you write back, that will help us keep our license database neat and tidy.