In the Windows 95 days (and probably in the Windows 2000 days, and maybe also today) "all" a screensaver was was an .exe renamed to -if memory serves- .scr.
There may have been some special interface that the program being run was expected to conform to so the screensaver subsystem would invoke it, but (IIRC) a screensaver could do anything an ordinary program could do. (That was the big reason for being cautious about where/who you got your screensavers from.)
In the Windows 95 days (and probably in the Windows 2000 days, and maybe also today) "all" a screensaver was was an .exe renamed to -if memory serves- .scr.
There may have been some special interface that the program being run was expected to conform to so the screensaver subsystem would invoke it, but (IIRC) a screensaver could do anything an ordinary program could do. (That was the big reason for being cautious about where/who you got your screensavers from.)