increasing user from 10 to more in IIS 5.1 server

I am getting a server time out when customer process an order on my web site. The order is comming over but customer dose not get a confirmation page just the time out page. I tried and also thought the order was not accepted. I was told that I am getting to much traffice for the server to handle. He also told me there is a patch to increase the user to 40 or 20 which he feels would correct the problem. Dose anyone have and ideas or know of this patch?