COM ports

I have a Win NT4.0 client. It graps data from other system through a serial cable. currently no data is transferred. It seems that com ports are not working any more. When checking the devices under control pannel, i found that serial service is stoped ( i think this is the cause of the problem if i am not mistaken). i couldnt start it manually. it gives the error mesaage [ the file specefied cannot be found] So is there a way to reinstall this service again ..? or shall i reinstall the O.S ..? What is the file to run this service..?