To save the Spectrum's display to a Windows bitmap or PNG file
On the File menu, click Save As.
Change Save as type to the format Spectrum Screenshot (.png;.bmp).
Type a name for the bitmap file and click Save.
Tip
For best results, pause the emulator so that the screen doesn't update before you get a chance to save it.
PNGfiles are recommended overBMPfiles as they are much smaller and better supported by modern applications.