Lan and Networking Problems

Hi,

I was hoping for technical support on LAN networking.

We have 4 Computers, 2 Printers and a Public 900gb Server on a LAN,
Running 1 Techni Color router and have encountered nothing but problems since
moving over to the new service.

The PC that i'm having a problem with is connected directly to the router but when i connect the Printer (Roland VP-540i) via ethernet cable to the router i can either get the printer working or get access to the Internet and Public Server but cannot get all 3 Services working at the same time.

Please Help.

Thank you for Replies in Advance any Help is greatly appreciated.

Dez