Don't even use the nodvd that came with Rewrite. You don't need it. Just do these steps (after you completely uninstall the game, might as well start over)
1. Mount disc 1. Run the setup. It'll start installing the game
2. It'll ask you to put in disc 2. Just UNMOUNT disc1, and MOUNT disc2. Just do the disc1 and disc2 stuff separately instead of trying to mount both of them.
3. Installation finished. Run the latest Rewrite english patch
4. Run Siglus. (don't use the nodvd, the english patch will make it so you don't need to keep the .iso mounted)
If Siglus isn't working at this point, use the Siglus that OMA provided earlier and replace that after step number 4.