How to take backup while services are ru

We are having windowsNT4.0 server and IIS server also running on the same machine. And we installed HP surestore DAT drive(8GB) external to take backup. While i am taking backup it skips some files that corresponds to that particular service. for eg:IIS. same thing for antivirus. What should i do to avoide skipping some files while taking backup. is there is any procedure is available. otherwise should i manually stop all the services before going to take backup. i am using windows default backup utility. pls. give solution.

regards
sakthi