Ok people listen up, I got a solution for playing Underworld. This will guarantee you playing the game with no cracks and shit. This method has been found completely by luck but works like a charm...
Get gamejack, install virtual drive, use virtual drive to install sacred and underworld (separate installs).Use the detect protection that gamejack has and then add both sacred and sacred underworld inside the "gamestarter".
When finished, leave the Underworld CD1 mounted on the virtual drive of gamejack.
3.Install nero burning rom. Install its own imagedrive and enable both drives. Mount 2 different isos (each on a different Nero imagedrive cd drive) containing some huge file inside them.
Fire up gamejack and set it to the "gamestarter" panel.
Now go to "My Computer" and open the first of the 2 nero imagedrive cd's, take the big file from inside and start copying it anywhere on your hard drive.
While that is being done, open the 2nd cdrom made by nero imagedrive and start copying another huge file onto your hard drive.
While these two tasks (copying..) are being executed, you cunningly switch back to your gamejack "gamestarter" and double click on sacred underworld (its the one with the underworld icon/light blue) and observe the magic of pure scsi emulation confusion!
--- I have no idea why all this works, but I don't care to mess around with the details as long as it works. 2 Other people have confirmed this. So I guess now its your turn. I guarantee that this method will be working 90% of the times you double click on the gamestarter icon of underworld. This means that if at first you don't succeed...keep on double clicking and at some point you will eventually skip the copy protection and enter the game smoothly..When the game begins, you can alt+tab in order to stop the "copying files..." of the 2 huge files (preferably a movie .mpg / .avi works great).
So don't be discouraged if it doesn't work all the time... For me and my buddies, it works 2 out of 5 times of double-clicking while transferring files from the nero imagedrives...
This game had broken our balls, and we just had to find a way to play it. I hope my trick, sheds some light to those with more knowledge in finally completing a crack for the damn game...