if you still have v3.7.3 installed you can use the backup/restore feature to backup your data and then restore it to v4.0
We have a step by step guide on our site at
http://www.flashfxp.com/forum/showthread.php?t=13507
If you don't have 3.7.3 installed anymore you'll need to either manually copy over the files or you could do a site import (Main menu > Sites > Import, from the import dialog select your 3.7.3 sites.dat file) however importing the file will only import the sites and not the rest of your settings.
Hybrid Mode
