In the event of a drive failure, Time Machine has the ability to create a bootable backup. It takes some preparation, however, which must be done before disaster strikes.
Using Disk Utility, create a partition on the drive you are using for Time Machine (see Disk Utility Help for instructions on how to do this without erasing your Time Machine backups). The new partition must be large enough to hold the contents of your computer's drive, plus 10 or 20Gb of elbow room. If your system weighs 85Gb, then the new partition should be 100Gb or so. Leave this partition blank, and go on with your [...]