I am going to guess you actually have a router rather than a modem since something is giving out the DHCP addresses to you.
I would just switch everything to DHCP, the ip's seldom change, if you need them to never change you can static DHCP assignments in the router.
If you really want to stay with static you must change the router IP address to match the range you are using. You also need to change the static settings in your PC;s to use the router as the gateway and maybe the DNS depending how you set things up
I have a 10 pc and printer network connected via a cnet CNSH-2402g swith. Each pc and printer has its own static IP address 192.168.0.X. We just had a broadband connection installed and I have a static ip from my provider. I hooked up the modem to the switch. If I use the staic IP info I can see all the network pcs, but cannot connect to the internet. If I change my settings to DCPH I can connect to the internet but can see the other pcs. Any advice would be helpfull...thanks