threading question

I have the following code in a windows service, when I start the windows
service process1 and process2 work fine , but final process (3) doesnt

called. i stop and restart the windows service and the final process(3)

called. what am I doing wrong with the threading? by the way
Directory.GetFiles(IncomingXMLPath1).Length is some global outcome from
process 1.

Thanks

1)
m_threadNewClaimInstitutional = new Thread(new
System.Threading.ThreadStart(process1));

m_threadNewClaimInstitutional.Start();

2)

m_ThreadNewClaimProfessional= new Thread(new
System.Threading.ThreadStart(process2));

m_ThreadNewClaimProfessional.Start();

//when all the files have been processed in both the process1 and process2
directories

//then is the final process

#)final

if(Directory.GetFiles(IncomingXMLPath1).Length==0 &&
Directory.GetFiles(IncomingXMLPath2).Length==0)

{

m_ThreadFinall = new Thread(new System.Threading.ThreadStart(process3));

m_ThreadFinall.Start();

}