Is this on your MacBook Pro? If so, the disks should work both legally and pragmatically. You wouldn't need to use bootcamp though, since bootcamp is designed just for Windows. Nevertheless, it's pretty easy. Here are the basic steps I would follow:
- Insert your install DVD. Shutdown your computer.
- Start your computer pressing the C key to boot from the DVD.
- Once in the installation assistant, go to Disk Utility under Utilities > Disk Utility.
- Select your disk. Select the Partition tab and click on the "+" to add a new one. Call it whatever you please, add at least 10GB of disk space (enough to install Snow Leopard), and make sure it's in Mac OS Extended (Journaled).
- Apply the settings. Go through the installer like you normally would, though when it asks you where to install it, tell it you want the Snow Leopard to be on your new partition.
This should let you boot on Snow Leopard by pressing the opt/alt key, just like when you boot Windows.
Hope it helps! Any other thing you need fear not comment.
To boot the computer, you need an already-formatted disk, which could be a DVD, a USB drive, or another hard drive.
If you do not already have one of these (and do not have another Mac that you can use) then your options are fairly limited:
Buy Snow Leopard on DVD. You can get it from Apple for $30, free shipping, but it won't ship for 3-5 days.
Buy DiskWarrior [$100] which is probably your best bet if you want to try to save the current hard drive.
Buy Lion on a USB drive $70 from Apple. Note that this is a terrible solution, IMO, because you will not be able to download Lion from the Mac App Store nor will you be able to use Lion's "Recovery Partition" (which, if you had it on your Mac, would most likely have solved your problem).
The rest of this answer is strictly opinion.
Personally I think your best option is #2 and #1.
DiskWarrior is an essential tool for trying to recover from hard drive errors. If your drive is having problems, I would not trust it for very long. Copy an essential files to another drive and then run DiskWarrior. Even if DiskWarrior is able to correct its errors, I would be sure to start making regular backups using either SuperDuper or CarbonCopyCloner.
The problem is that if DiskWarrior finds problems that cannot be fixed, then you are going to need to replace the hard drive and reinstall Mac OS X… which means that you are going to have to buy Snow Leopard on DVD (assuming that you don't have a friend who can make or loan you a copy).
The $70 USB stick from Apple is a terrible deal. If you want to move to Lion, buy your own USB drive, find a friend with a Mac, ask them if you can use it to buy Lion from the Mac App Store, and make your own Lion USB drive using one of the many how-tos posted online, such as this one from TUAW.com.
Best Answer
Is it humanly possible, if you received an ISO from some source, that you could create a burnable disc from a PC? Yes, no reason why not. That being said, if you have upgraded the firmware on a recent-enough MacBook Pro, and have a fast enough connection to pull down a OS install disc, you could use internet recovery:
Apple's Knowledge Base Article for Internet Recovery-Capable Macs
I believe this won't work if you hadn't run this updater on your Mac after already upgrading to Lion, but it would pull down a recovery partition of less than a GB first, from which you could at least browse the web with the 'get help online' Safari Kiosk mode, or go on to do a full reinstall.
Beyond the 10.6 disc, there is also a USB drive for Lion that can be purchased as well, of course. Good luck