The photos you can just leave where they are, as long as the drive letter remains the same between installations (it's possible to change the drive letter of a volume, if necessary, in Disk Management).

As for the catalog, the surest way to back it up is to use Lightroom's built-in catalog backup functionality - follow the instructions on this post (Joe Barrett, The Image-Space, "Lightroom Tip - How To Change The Default Backup Location") to set the backup location to a directory on your other drive and invoke a backup immediately. I recommend leaving this option turned on, to protect against catalog loss due to Lightroom crashing and leaving the catalog in an inconsistent or corrupt state.

To restore the backed up catalog, you just need to copy the backed-up catalog to some location on the newly formatted drive, then open it in Lightroom with File->Open Catalog.

To protect against inevitable disk failure, you should also copy both your photos and the backed-up catalog files periodically to another disk and/or to online storage. Using RAID 1 (mirrored disks) for storing your data is a good idea, but does not protect against human error (accidentally deleting everything) - so regular backups are essential.

See also this guide (Rob Sylvan, Lightroomers, "Migrating Your Lightroom Catalog and Photos to a New Computer") for a slightly different approach with screenshots. If you have custom presets this guide will explain how to transfer them.