Using a separate partition on the same drive as the system is not generally recommended, as a very common, if not the most common reason, for needing a backup is the mechanical failure of the drive. When this happens, quite frequently nothing on the drive is usable.

If one buys a new hard drive, it should come with software that allows you to "mirror" the existing drive onto the new one, thereby making an exact copy of the existing installation. My experience has been that the computer doesn't know anything at all has happened if you swap drives between an original and a true mirror.

The backup (or backup and recovery) system built into recent Windows versions has placed on a "Recovery Disk" all the "program" needed to boot from the disk and transfer the whole program back to the same drive it came from or to a new hard drive. If your Windows installation isn't working, there's little rationale for making a backup; and if it is working there should be no problem with using the properly created backup for a reinstallation.

A rational procedure would be to follow the Microsoft instructions for making a "Recovery Disk" just in case they might actually know what works. If you really want to "do a little extra," after you've done the RTFM and made a recovery disk, using third party products for whatever suits you is fine.

While I didn't easily find instructions for making a backup, the inserted instructions within the KB article linked above should take one to exactly the same place in Vista suggested by Joe O.

What I did find in my brief search at Microsoft was a long list of individual articles on "how to recover from failure to reinstall from backups made using other methods¹ or products."

¹ One problem is that a few Vista system files apparently are encrypted and self-destruct if just "copied." A second is that many third-party "backup" utilities ignore and don't automatically backup temp files. At least one such temp is documented as being required for a successful system restore, and as being frequently "lost" by a couple of popular third-party "backup" programs.

Do note that the Backup system built-in in Vista allows several different kinds of backups and/or "backup modes," only one of which apparently will be useful for a "full system restore." Reading the instructions when you get there should make it reasonably straightforward to choose the right one.

John