Usually the compiler error will say what identifier is undeclared and indicate where it is first used.
If you have not declared it earlier (e.g int i) then you'll need to add the appropriate...

For a discussion of detecting cycles in linked lists, see http://ostermiller.org/find_loop_singly_linked_list.html

-bobd-

A little further searching for _WIN32_WINNT in the VS7 help index brings the following.

[Begin help file text ]
Certain functions that depend on a particular version of Windows are declared using...

I took a quick look at the code then tried to compile under VC7.1. It failed there too. I right clicked in the IDE to find the definition of INPUT which took me to WINUSER.H. Everything looked ok...