When that's done, update to Windows 8.1 Update through Windows Update. The last Windows 7 service pack is SP1, but a Convenience Rollup for Windows 7 SP1 (basically an otherwise-named Windows 7 ...
Yes, you can download Windows 7 ISO files for free directly from Microsoft's servers. All of them are Service Pack 1 (SP1) ISO files and are roughly 5.5GB in size. Download the correct ISO file as ...