I have discovered on an obscure web forum that in 2007, a Microsoft employee sent via private email a hard-coded universal product key for Windows 98. Apparently, no one was able to find this through reverse engeneering. I have tried the key on two seprate ISO files of Windows 98, and believe that this man is telling the truth. I do not know if there are limitations to this univeral key. The key is as follows:
VP9VV-VJW7Q-MHY6W-JK47R-M2KGJ
This information was retrieved from a webforum called
wugnet.com Dead link
Alternative here.