I don't have any experience using the Windows Installer of Ubuntu, so please don't be offended if I write total nonsense.
If I'm not mistaken you installed the Ubuntu boot manager (grub2) on your HDD in order to use it to load Ubuntu from the Ubuntu CD. Since your Ubuntu CD is not a physical disk, but a CD image that you mounted in a virtual drive emulated using a Windows program, the boot loader (which is executed before any OS is loaded and therefore also before any virtual CD drives are available) cannot find the CD and therefore fails to load anything from it.
My suggested solution is simple: Burn a real Ubuntu CD and boot from it, either by using the boot loader already installed on your HDD, or by simply booting directly from the CD using the boot device selection option of your BIOS or EFI (actually that's the preferred way and what you did, installing the boot loader to hdd, is only meant as a workaround for the few computers that cannot boot from CD). Of course you can as well create a Ubuntu Installation USB pen drive by using Unetbootin or a similar tool.
If you want to uninstall the Ubuntu boot manager and go back to Windows only, you probably have to rewrite your HDDs master boot record. On Windows 2000 or XP one can for instance boot from the Windows CD, go to Recovery Console and run the fixmbr (or was it fixboot?) command. For newer Windows versions there exist similar commands.