I would start with some very small basic models and see if you can get those to render, slice, and preview properly. Something like a standard 40mm cube. Then start working your way up to more complex models. If the simple models work fine, but the larger ones start to cause issues, it gives us an idea of what might be causing the problem.
And I would absolutely suggest switching to the "Low detail" preview type (in Tools > Options) since that uses much less memory than the full 3D preview.
And try to resist the urge to always force quit Creator if you get a "Not responding" message. Many times that is just because it's in the middle of a calculation that probably only takes a fraction of a second on a normal computer, but might take a few seconds to complete on a really low-end machine.