Been using Irfanview since it came out in preference to everthing else.
- When you open an image in a directory, in IView, just hit the Enter key to switch to Full-screen.
- Then hitting the space-bar will scroll through the directory in full-screen mode. to leave full-screen, just hit escape. (Thereare other ways too including use of the up/down/L/right keys/
- Regarding your resizing problem, go to the View/ Display menu in IView. There are tons of options for display there. For example you can change a window size by dragging diagonally at the to-corner of your IView window, and if you have set the setting above in view-display to "Fit to Window", you can dynamically drag the window from thumbnail size to full screen and back.
- You and others are probably aware of another Windows "trick" - which works well with Irfanview. Fix your Window at the size you like, close it (Top-rightX) -WHILST holding the control key. When you reopen it it will be right size and in exactly the position you left it.
- Finally it is worth trying all the other options in that display menu.Depending on the format of your screen, browsing through directories of pictures might be better in fit to desktop height or width.