I don't mean to be disrespectful, but it's not a case of my machine simply being underpowered. It's an average modern-ish machine, and certainly doesn't take ten seconds to create a bitmap in memory under normal circumstances. It is an issue with Paint.NET reacting unhappily with something on my machine, and possibly others - it's not that I don't have a fast enough CPU or not enough RAM.
The OS and graphics card are relevant details, as it may be a configuration issue. XP & Geforce 2.