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.)
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.)