sendmail/qpopper failing unexpectedly

i all. am running a RH 9.0 based mail server (sendmail-8.12.8/qpopper) on an intel Celeron based system. After install and config, it will work fine for 2 to 3 weeks and suddenly stopps sending/receiving. have checked the server (log files, config files...)but. made several tests, swapped systems and used AMD based systems to no avail. rather, every time before reinstall find bad sectors on the hard disk and the install aborts. swapped HD several times, restarting the install/config processes all over but no luck. wonder if it's a hardware issue or a software issue!
any clues? thanks.

angelo.