Thats very very odd. Its should ask for serial at least the first time you install it. When you uninstall it make sure the folder directory for hexagon is gone, if not delete it. You may want to go into regedit and remove anythink related to hexagon. of corse back your regestry up and do that at your own risk. If all goes to fail you could try installing another copy of windows on another HD or partition, I have another copy for testing stability and bench marking.
You may want to take this to the hexagon section of Daz3d forum where others can also offer some advice.
Good luck.