Since you've told us nothing about your computer, your network, or the
device that is doing DHCP - all we can do is guess. My guess is that the
static IP address you assigned is inside the address range of the DHCP
server's and therefore something else is getting that IP address first.
Static IP addresses should be outside the DHCP server's address range.
IOW, if your DHCP server's address range is 192.68.1.10-200, give a static
IP of 192.168.1.230.
Thanks for the response. The DHCP server is a ZYXEL ADSL/router P-662H and
the PCs are HP dc7800s. All PCs are configured to static IP different from
the DHCP range. Static range from 192.168.1.2 - .200; DHCP range from
192.168.1.230 - .246.