char tmpnum[1];
char ID[10] = "";
int rndnum;
int x;
for(x = 0; x < 10; x++){
    srand(GetTickCount());
    rndnum = rand()%9;
    sprintf(tmpnum, "%d", rndnum);
    strcat(ID, tmpnum);
}
printf("Random STR: %s\n", ID);