В посту выше написано, что можешь получить бесплатно имидж Виндоуз при регистрации с ними. Сначала проделай эти шаги, а потом уже замени шаги по инсталляции Виндоуз на те, что ниже тут.
http://download.parallels.com/desktop/v9/ga/docs/pt_BR/Parallels Desktop User's Guide/32731.htm
Install Windows
If you have a Windows installation source (a DVD disc, an image file, or a USB storage) and a valid Windows product key, you can install Windows on your Mac and use it with Parallels Desktop.
To install Windows:
Open Parallels Desktop (in the Applications folder) and choose File > New.
If you have a Windows installation disc, insert it into the DVD drive. If you have a USB storage with Windows, connect the storage to the Mac.
Click Install Windows or another OS from a DVD or image file.
Parallels Desktop scans for and lists installable operating systems. If you see the version of Windows you want to install, select it, click Continue and go to step 6.
If the Windows installation source didn't show up automatically in Step 4, click Locate manually to browse for it manually. You can browse from the following sources:
DVD: If you have a Windows DVD, insert it into the DVD drive. Once Windows is detected, click Continue. If your Mac doesn't have a DVD drive, you can use an Apple SuperDrive, another Mac's DVD drive via Remote Disc, or make an image from the disc.
Image File: If you have a Windows image file, click Image File and drag the image to the Parallels Wizard window. Once Windows is detected, click Continue.
USB Drive: If you have a bootable USB installer with Windows, click USB Drive and connect the drive to the Mac. Once Windows is detected, click Continue.
Note: Parallels Desktop may fail to detect some operating systems (for example, the latest Linux distributions). If this happens but you're sure that the operating system can be installed, click Continue, specify the OS type manually (if it's not listed, choose Other), and follow the onscreen instructions.
Be sure to leave Express installation selected.
Note: If you deselect Express installation, you'll need to install Parallels Tools after the installation to allow the most seamless operation between Windows and Mac OS X.
If you are installing a recent version of Windows, select how you want to use Windows:
Like a Mac: Windows programs appear on the Mac desktop, just like Mac applications. Documents and media from Mac OS X and Windows are kept together on your Mac.
Like a PC: The Windows desktop and programs appear in a single window, separate from Mac applications. You can drag and drop objects between Windows and the Mac.
If you are installing Windows 8, select how you want it to work:
Like Windows 8: Windows 8 boots to the Start screen and Windows 8 applications run in full screen only.
Like Windows 7: Windows 8 boots to the desktop, Windows 8 applications run in resizable windows, and the Start menu is available.
Choose where you want to store Windows from the Location menu.
By default, Parallels Desktop stores Windows in your Documents > Parallels folder. To allow all users of your computer to have access to this installation of Windows, select Share with other users of this Mac.
If you want to pre-set things like how much memory Windows uses or whether it starts automatically when you open Parallels Desktop, select Customize settings before installation. You can also adjust these settings after the operating system is installed.
Click Continue.
The assistant installs Windows.
Once Windows is installed, you can start it up by opening a Windows program or by clicking the power button in the Parallels Virtual Machines list.
Important: The first time you start Windows, Parallels Tools are installed to allow seamless operation between Windows and Mac OS X. Once Parallels Tools are installed, you're prompted to restart Windows.
If you didn't select Express installation in step 6 above, you must install Parallels Tools manually.
When you install Windows, Parallels Desktop creates an administrator account with a blank password. Once the installation is complete, it is recommended that you change this password.
Note: You can also install Windows from a disk image file of an installation disc. Simply choose the disk image file in step 4 above. Parallels Desktop supports ISO, DMG, CUE, and CCD disk images.