Here's a couple of things I have found out about this issue. First, this problem has little or nothing to do with Boot Camp. I managed to install Windows 7 on my Mac Pro on its own dedicated drive without the use of Boot Camp.
I found some of the instructions that are our there for this problem fixer a little vague. It took me quite a bit of time and several failed tries before I was able to finally get this to work, but it does work. Now you don't have to make the same mistakes that I did, just follow this step-by-step process which is what I finally did to make it work.
This method is used to create a new install disk if you have your authentic Windows 7 disk. Don't sweat it; it's much easier than it looks.
*Note: you will need to do this on a PC*
In your C drive, create these two folders: c:\windows7exe c:\windows7dvd
Go to this link
http://rapidshare.com/files/297067205/oscdimg.exe and download Oscdimg.exe. Place it into c:\window7exe folder
Insert your Windows 7 disk into your DVD drive For this example, we will refer to it as the D drive.
You need to open a DOS prompt window. Do this by going to start/programs/accessories/command prompt
Your default command prompt will look something like C:\Users>.
At the prompt type cd c:\windows7exe
Your command prompt should now look like c:\window7exe>
At the command prompt, type in exactly (or copy and paste):
oscdimg.exe -n -m -bd:\boot\etfsboot.com d:\ c:\windows7x64.iso
+Note: the letter d in the above command refers to your DVD drive, change it if your DVD drive is labled with a different letter.+
Press Enter. This will begin creating a new disk image. You should see a response in the DOS window that displays its progress.
When the process is complete, you will find a new disk image of your Windows 7 disk in the folder labeled c:\windows7X64
Now that you have a new disk image, you need to burn it onto a disk using ImgBurn. This is a free utility which you can download from here:
http://www.imgburn.com/index.php?act=download
Place a blank DVD into your DVD RW drive.
Launch ImgBurn and select "Write image file to disc". In the Source window, find your newly burned image in the c:\windows7X64 folder. Click on the disc icon at the bottom of the window to begin the burning process.
Voila! You have a new Windows 7 installation disk which will install with no problems.