troubleshooting services

Hi,
i am having a problem with a machine runing on windows ME.The problem when i boot into the machine its starts properly and after few minutes it hangs and when i check for the problem in task manager its says one service is not responding and when i close it and start my work and after few minutes it again shows me that there is another program stoped responding.i checked for viruses and nothing is found out.There are important files on that system so it cannot be reinstalled can any one guide me with this issue,thanking u in advance,hope i get a reply ASAP.