You may not be able to copy the disc successfully. Microsoft use blockers in other software so perhaps Windows 7?
Well, technically, it won't successfully go through Product Activation unless the product key from the lost disc is used (and of course, that product ID will need to perfectly match the edition of Windows 7 - in other words, a Windows 7 Home Premium Retail Product ID won't work with Windows 7 Ultimate OEM). It will install, but it won't activate and you'll only have a usable copy for about 30 days until it deactivates and is useless.
Boot Camp has changed a little bit in recent months. It now prompts you to burn a disc during the partitioning process, but first it will need to download that package from the Internet. This disc comes with an updated suite of drivers for newer Macs. Since you mentioned that you're not in a position to download anything, I'm going to guess that you skipped that step, and instead assumed that your OS X disc would have the needed drivers.
Now I'm going to jump to another conclusion here - and that is that you're not using your original OS X disc. And if that's true, it might be another cause to your troubles.
What I would do if I were in your shoes is this....
1. If you can't find YOUR Windows 7 disc, contact Microsoft and see if you can get a replacement. Since you apparently have your registered product ID, they may be able to accommodate you.
2. Run Boot Camp Assistant again and revert to a single partition.
3. Find a Starbucks (or another place with free WiFi) and connect to the Internet. Make sure you've got a blank DVD handy.
4. Run Boot Camp Assistant while there and allow Boot Camp Assistant to download the driver package and burn your disc.
5. When prompted to reboot from your Windows disc, opt out so that you don't have to spend the next 45 minutes sitting in Starbucks (unless you've found a particularly comfortable seat).
If you can't do one or more of these things, I'd recommend holding off on a Windows install until you can.