waves.com and register your v4. Once you do this, your Waves account area should">

Pro Audio Support

Q:
I just purchased Waves (insert product name) v4 and I notice v5 is now available. Is there an upgrade path?
 
A:
Yes! Simply go to waves.com and register your v4. Once you do this, your Waves account area should show a link to the corresponding free update to v5. Be sure to read the list of qualifying hardware and sofware before upgrading, as some specifications have changed between the two versions.