I have two desktop computers and i want to connect them to my modem what are the steps to take and if i want addition hardware.

What kind of modem? Dial up? Or cable/DSL?

If cable/DSL, I recommend a simple Ethernet router. These allow you to connect multiple computers to one modem, but they also offer a HUGE security advantage of hiding your computers IP address from all but the most serious badguys. They do this by the router assuming the IP address assigned by your ISP, then the router assigns new IPs to each connected computer. The router also allows you to connect a network ready printer to your network so any computer on your network can print to the printer. The printer does not need to be tethered to a computer, so no host computer needs to be up and running for others to print. Many printers come network ready or you can buy a print server that connects the printer to a network. Or some routers have a print server built in.

Will i get the same speed on each PC Say speed is 600 Kb/s will each PC get 300 Kb/s or the same 600 Kb/s (using 2 PC) is a Ethernet router the same as Ethernet switch

Your network (everything on your side of the gateway device - the modem) will run at Ethernet speed - which is at least 10Mb/second so that's not a problem.

Router vs Switch - What Is The Difference Between a Router and Hub or Switch?

Basically the difference comes down to with a switch any computer connected to it gets an ipaddress from the ISP (internet service provider) whereas with a router the router gets the ipaddress from the ISP and sets assigns ipaddresses to all devices connected to it. Now depending upon your ISP you might need (or at least benefit) from the router as compared to a switch because you are only getting one ipaddress from the ISP. I say this because with our ISP from our monthly payment we get 1 ipaddress and if we want anymore we have to pay an extra monthly fee per address. I'm sure that there are others that have a similar policy. If yours has such a policy a router will eventually pay for itself.

If yours has such a policy a router will eventually pay for itself.

And offer much better security.

thanks