Well, the explorer_new.exe does not work. It does nothing at all, that's not my issue. The explorer.exe program takes forever to show the files in a folder on a virtual machine (like "My Documents"). This can be understandable, however when you Resize the window, explorer.exe recalculates what it should be displaying. So for every pixel of difference in size, you have top wait 3-5 seconds before explorer.exe starts working again, because it's calculating.
I wanted to test ReactOS on a slow-ish machine, so I have it in VirtualBox with 2048MB of RAM and 32MB of video memory, running on a single 3.4GHz core. (I don't know if this info is useful, but you never know)