You’ll need to purchase a third party backup solution as none of the native backup tools work with Exchange 2007. You can also setup a 3+ node CCS cluster (the cluster that doesn’t have shared storage) then you really don’t need to worry about it as the chances of all three servers failing at the same time are minimal (this is what Microsoft does with their production Exchange 2010 systems).
I agree with MrDenny. There are various flavors on which you can protect your Exchange infrastructure from disaster. A simple viable option would be to install a 3rd party product like XoSoft High Availability which would make 2 servers identical to each other. I recommend you install this “standby” server in another office not in the same geographic location as your primary (DR 101). The software would replicate changes to each other. The software has the option to “test” of failover so you can test DR periodically which is always a good audit report for management. When servers failover, Outlook clients would be redirected to the new servers automatically.
Then you would need to purchase a 3rd party backup solution like a NetBackup, Legato, etc. to backup your Exchange to tape.
This will help provide a nearline recovery as well as DR recovery (offsite server as well as tape if needed).