I just tried to replace all [NUL] values in an Excel document (74 kb - there are quite some [NUL] values in it) but HiEditor keeps crashing as soon as i switched to an other window/application.
It does not really crash but it turns "not responding" when i try to reactivate the HiEditor-window again.
It's also not possible to "Cancel" the replace-process.
Maybe someone can give it a try to reproduce this behaviour?!
But anyway, it's nice that HiEditor can replace these characters like [NUL] (not all editors provide this feature).
I don't know if this is possible but maybe you can disable something like "Application.ScreenUpdate" while replacing.
This would mean that HiEditor doesn't show the replaced characters and it's progress before it's completely done.
This should speed up the replace-process as HiEditor does not have to update the screen, the caret position and all that before it's done.
At least in excel-macros and VB this helps
But as i said, i got no idea if this is easily done in HiEditor.