In reply to veteye:
I didn't misunderstand - you didn't explain what you actually did. I've learnt to never underestimate what people 'actually' do with computers
Been using LR since V1 Beta, so yes lots of experience with it.
I run a master catalogue with 63,000 images spread across many folders, 5 separate internal/network drives: so I wouldn't worry about them being in one 'Master' folder location, but it is easier from a management/structured approach.
The recommend approach is to have your catalogue on a separate drive to your images and to your OS (mine resides on its own SSD), and don't put images on your OS drive: these approaches help to make LR work faster (supposedly).
If you want to physically save the image changes you made within LR (LR is non-destructive), then you'll need export the images you changed to new files as the originals will remain unchanged; the metadata may change - if you set up LR that way (most people don't as it slows down LR), but the changes will only be manifest when the images opened within programmes that read the metadata image adjustments (e.b Adobe Bridge).
And have installed and reinstalled quite a few times (!) over the years. You shouldn't have any issues.
Installing/reinstalling won't alter/delete your LR catalogue, but it may create a new one.
If you have not set up LR to save changes to the image metadata, then when you create a new LR catalogue and re-import all your images, then the LR changes you made in your original catalogue wont show up in your new Catalogue.
But you shouldn't have to reinstall to change your folder structure, but it 'could' be a pain-in-the-**** if you have to re-point your LR catalogue to lots of new locations (it usually does a good job once you point LR to the top level folder location).
Drag and drop does work within LR, but I'd be very cautious about moving lots of folders around within LR - be careful.
To add: If LR can't find the folder location, then the folder still shows up, but with a ? next to it. Thumbnails will also show up in Grid Mode - LR stores image previews.
Post edited at 14:58