It looked like Microsoft was finally going to do the right thing. Beta versions of Vista SP1 came with a modern equivalent of the old Windows Boot Floppy--a Start Menu option called "Create a Recovery Disc" that burned a Windows PE-based emergency CD. Alas, Microsoft removed that feature before SP1 shipped, but not before NeoSmart turned the disc into an .iso file and made it available on their site.
Running on the Vista version of Windows PE, the Recovery Disc is basically a Vista installation disc minus the install files. It even has an "Install now" button that asks for a Product Key before failing. You're better off clicking the Repair your computer button. Among its Vista-only options are a tool for diagnosing and fixing startup problems, a version of System Restore that uses restore points on the hard drive, the restore portions of Vista's backup program, and a memory diagnostic tool.
Note: This link takes you to an external Web site, where you can download the latest version of the software.