Hex Workshop can open files up to 2 gigabytes in length, however, you must have ample disk space available for temporary work files. Please make sure you have disk space (2 times the size of the original document) available on the same drive as your windows temporary directory.
There are a number of preferences related to this topic:
Temporary Files in Paths Tab: If you do not have enough disk space on the same drive as your windows temporary directory then you can set a different work drive and directory for Hex Workshop.
Postpone write initialization in Configuration Tab: Hex Workshop can either create a working copy of your file when it is first opened or at the first write attempt. Checking this option will postpone creating the working copy until an operation tries to change the document.
Enable direct file editing in Configuration Tab: This option tells Hex Workshop to edit files directly and not to create a temporary working copy of your document. Please make sure you backup your documents before enabling or using this option as you may damage your original file. Hex Workshop will still need to create temporary files when insert and deleting.