There's programs, like Recuva
, that'll read through your hard drive and restore what it assumes to be file and folder systems, so you can just tell it to restore your ROM hacking folder and voila, there's your level.
I once used Recuva on a Computer I had to format because I needed a certain very large folder back, and Recuva did that for me pretty quickly.
Well, relatively quickly, finding the files was no problem but it took like 20 hours to restore them all. Though that should be considerably less for just your VLDC rom.
As Vitor said, this works because an operating system reinstall doesn't actually delete everything on your disk, your OS (assuming Windows) just "forgets" where those files were, so it can't show them to you.
That's where these recovery programs step in and just look at all the data it can find lying around and shows you what it finds.
edit: Also, take this as a lesson to ALWAYS back up your projects somewhere online.
Just upload a .zip of your hacking folder to Dropbox every day or so and hard drive failure will never make you cry again.
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