You can download an ISO of Win 7 Pro from Microsoft. It can be used to repair boot error if that is the problem you are currently having. I assume can be used for 90 days without entering a product key. Of course, it can be fully activated as long as you enter the product key which should be located on the underside of your laptop.
The product key must match the Windows 7 version, meaning you cannot install and activate Windows 7 64-bit Ultimate if your laptop's product key is only for Windows 7 64-bit professional.http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_install/digital-river/66a8439b-0d16-4b70-92f7-1c8486a46ebf