Hi, press CTRL+F12 to toggle fullscreen mode. Or you can double-click on its title bar.
If you press F12 there are more options to enlarge the size even more.
I suggest you try the following from WinUAE options:
Miscellaneous - change Graphics API from DirectDraw to Direct3D (you may need to update DirectX)
Display - change Fullscreen display mode to the highest supported by your monitor
Filter - Point/Bilinear - change slider to 1 to smooth the scaling
Filter - change "No scaling" to "Fullscreen (Max)" and try playing with the sliders to use up all your monitor...
Since you're using my emulation pack for AMOSPro, when WinUAE 2.4 is released I'll do a new version which will support Vsync (smooth scrolling) while using the JIT compiler and AROS ROM. That will enable things to scroll smoothly when using the emulation pack.
Currently, if you want to save the config file for my AMOS for Windows emulation pack (it uses a custom launcher for WinUAE), such as to get fullscreen each time, you need to remove the ROM images from the configuration before saving (go to ROM and delete both lines), and remove the mounted hardfile (go to Hard Drives, click on the mounted drive and select "Remove"). Then go to Configurations then "Save As" and overwrite the AMOSPro.uae config file in the AMOS for Windows directory. The next time you launch my AMOSPro launcher, it will add the hardfile and AROS ROM images when launching WinUAE (which is why they need to be removed from the config file). This will be simplified in a new release.
P.S. To get back to filling the window as above in windowed mode, simply go to Filter, click "Reset to Defaults" button, and select "No scaling" from the slider below.
Oh and nice rename for the Windows 7 trash icon.