Is it safe to delete library folder in Unity 4 (4.5 pro) especially as I've backed up the folder?

Basically I'm experiencing some big error/bug (key not found in directory etc.) followed by "compiler can't execute" etc. The result is that I can't build or hit play. And on top of that the whole project is about 17gb, 3d fps - I need just 2-3gb of these 17gb but they're still "stuck" in Unity as I haven't deleted them.

The only solution so far that worked was to reimport all assets - yet this works for 10 minutes or so and the error appears again for no reason. I think it's problem with my ram/hard disk and unity can't read something. It's very annoying bug. I now deleted the library folder while having it backed up before that, will this destroy the project or fix it temporarily at least? It takes 5 damn hours for this operation to complete...

If this doesn't work but at least I have the scenes in tact, I am planning to do it the slow way and simply write down the xyz of all objects + remember which objects have attached scripts to them and then start all from scratch, it should take abother 5 hours to re-create everything but only if the deletion of the library folder doesn't break the scene coordinates/everyhing in the scene. thanx