Windows 7 Download error - CDBOOT: Couldn't Find BOOTMGR

I'm downloading Windows 7 Professional from a disc. I downloaded the support software to a USB flash drive using bootcamp, and that all went fine. Then I chose the partition size, put in my Windows 7 disc, it partitioned & rebooted, and I thought it was supposed to boot up to the Windows installation. But it comes up with a black screen with a flashing prompt up in the upper left corner. So then I read on further in the bootcamp instructions & it said if I had problems restart the computer holing the option key, which I did. The screen comes up with the choice to pic MacHD or the Windows CD. I click on the Windows CD & it goes to another black screen, but now up in the upper left hand corner it says CDBOOT: Couldn't find BOOTMGR. So then I talked to an Apple Senior Tech & he told me the Windows disc had to be damaged or no good. So I went to the place I bought it & they gave me another copy. I came home & restarted my computer again holding the option key, selected the Windows CD & the same error comes up! I can't imagine having 2 bad copies of Windows 7. So what could the problem be? PLEASE HELP!!! Thanks!