It is always a good Idea to switch to windowed Mode before an other exe is called, because only the windowed mode will allow cross-app multithreading. Only system-hooking tasks like antivirus apps or firewalls or any other low level interrupt-driven TSRs can run in the background of a fullscreen Blitz App AFAIK.
The problem with switching to windowed Mode is all Graphics and Fonts get "lost" because Blitz performs an Endgraphics automaticly. So if you want to continue the App/Game after switching back to Fullscreen then you might have to reload everything. If you have a nice LoadAll() Function, or maxbe a Save- and Load-Game Function that can save any Stage of a Game then it isn't a problem.
BTW: If you want to start an external Exe and then End the running App, the only way is to switch to Windowed Mode, then ExecFile the File, then End. It is a good idea to ask windows what resolution the Desktop is running, then use this Size for the window size, so there will only the Borders popup. Many commercial Games do this as well.
The problem with switching to windowed Mode is all Graphics and Fonts get "lost" because Blitz performs an Endgraphics automaticly. So if you want to continue the App/Game after switching back to Fullscreen then you might have to reload everything. If you have a nice LoadAll() Function, or maxbe a Save- and Load-Game Function that can save any Stage of a Game then it isn't a problem.
BTW: If you want to start an external Exe and then End the running App, the only way is to switch to Windowed Mode, then ExecFile the File, then End. It is a good idea to ask windows what resolution the Desktop is running, then use this Size for the window size, so there will only the Borders popup. Many commercial Games do this as well.