You could write some code that would use Sleep() if compiled under Windows, some DOS function (delay()?) for DOS, some UNIX function for UNIX, and failing everything, a loop which eats the CPU but at least keeps your program running at the right pace.
Code:
#ifdef WIN32
#include <windows.h>
#else
#include <time.h>
#endif
void delay_seconds(int seconds) {
#ifdef WIN32
Sleep(seconds);
#elif defined(unix)
/* ... */
#else
time_t start, now;
time(&start);
do {
time(&now);
} while(difftime(start, now) / CLOCKS_PER_SEC <= seconds);
#endif
}
Something like that.