internet sharing connection

recently, i had set up an ics (Internat sharing connection) between two pc which is running on window ME. i found that the host machine will automatically dial up after certain time frame. Initially i thought that was cause by some software on the host or the client machine request for dial up, but after i check evything i don,t see there is any software called for dial up (i even look into the e-mail software). Please help me to solve this problem.