Hope somebody can help

I am new to Linux but somehow managed to install and get Apache and
vsFTP to work on Linux 8.

But after each day (approx 24 hrs), the system get lots of errors
shutting down and wouldn't again boot up. The messages on the boot
screen has quite a few "segmentation faults" and hangs as it is doing
"Enabling local filesystem quota".

When this happens, I had to reinstall the system from CD again. (The
problem does NOT arise when I am shut down immediately after I
installed it. Seem like something corrupts the system after a while).
The server has a static IP but runs behind a firewall.

What is going on here. I am running a Pentium III with 500MB RAM. The
apache run with digest authentication.

Thanks in advance.

JJ