There's one immutable law of PCs: sh*t happens. And when it does, there's usually a way to fix things, if you had the foresight to create one essential recovery tool first. Booting from a USB recovery ...
Windows 7: If you run into a boot-up error with Windows 7 and don't have a recovery disc handy, you're usually in for some manic fiddling, or you're just out of luck ...
I have a laptop running a fully licensed version of Windows 7 Ultimate x64. For some reason, the boot partition has become corrupted. I didn't get a Windows 7 disc or a recovery disc with the install.