Lightroom Catalogs

[marioval]

I know this is a video website but I get so much help on my video questions I though I would take a crack at an image question. I'm sure there are many of you here that use Lightroom so any help will be appreciated. My question is about how the lightroom catalog works. My default catalog is located in a folder called D:\LR\Catalog. Every week LR asks me if i want to backup my catalog and I say yes. It then creates a new folder named by the current date and time like D:\LR\2008-01-25. Now, my default catalog is about 300MB in size but each backup is only about 13MB. My question is this. If my Windows installation on the C:\ drive bombs and I have to reinstall. Which catalog would I use to get back to where I was before the crash. is there different data in the 2 catalogs? Do I have to do some kind of merge? is the small backup just a way of pointing LR back to my original catalog? Is the small backup just an incremental back of changes since the last backup, if so how the heck would I get all my changes back into LR? Thanks.

[guns1inger]

Lightroom's changes are non-destructive. That is, it does not change the original image, or store a copy of the image with your changes. What is does store is meta-data about your image, including keywords etc, and any changes you may have applied. The advantages are less disc capacity required, and the ability to come back and make changes in multiple sessions without degradation of the image. The backup includes on the meta data, so you need your original catalog of images, plus the last catalog backup to get back to where you were before a crash.

[marioval]

So on a fresh install of windows and LR, all I need is that small 13MB catalog file? What is that other 300MB then? What if that is lost?