CreateMutex

#include<stdio.h>
#include<Windows.h>
BOOL IsAlreadyRun(){
	HANDLE hMutex=NULL;
	hMutex=::CreateMutex(NULL,//改句柄不能由子进程继承
		FALSE,//不属于任何线程
		"lock1");//锁名称
	if(hMutex){
		if(ERROR_ALREADY_EXISTS==::GetLastError())
			return TRUE;
	}
	return FALSE;
}
int main(){
	if(IsAlreadyRun())
		MessageBoxA(NULL,"Process Already Run!","Message",NULL);
	else
		MessageBoxA(NULL,"No Process","Message",NULL);

	return 0;
}