Background: I have a desktop acting as the server for my home network, using a switch. ATM only my laptop is connected to the network by ethernet.
Problem: Starting a couple months ago, when playing World of Warcraft on the desktop, the dial-up disconnects. This is after about 30 seconds of logging on. It also disconnects when downloading.
When playing on my laptop, the connection holds, and I can play for hours.
I thought it was the modem, so got a new one. Not it.
I thought there was a virus, or something, so I ran several utilities. Still disconnects.
I even bought another hard drive, formatted it, put on Winxp, same as the old hard drive, and it still disconnects.
I've had the phone company check, and they say it's fine. I had the isp check their end, and they say it's fine.

Any thoughts?

it's probably not a virus. Some program (more than likely your game) has sent a drop carrier command to your modem.
There are quire a few programs out there both commerically and open-source that can keep your modem ON until you turn it off manually.
I know Norton utilities 2003 will.

most modem viruses will keep your modem ON to dial 1-900 #s or overseas calls.
As most people don't use dial-up anymore, the likelihood of it being a virus is slim.

What open source programs?
btw, It didn't used to do that, even playing WoW, now it does.

verify the modem settings do not have "disconnect after X minutes of inactivity".

to keep the line "active" you can always use the CMD prompt to

ping -t $your_isp_domain

(eg: yahoo.com)

First of all, thank you both for replying.

I did the ping and I get : request timed out.
over and over. lol

it doesn't really matter, unless you really have a connectivity problem.
The object is to keep packets flowing from you to at lease your ISP.
suggest you verify the connection via

ipconfig /all

which shows non 0 addresses for Ip, gateway, and dns addresses and a mask like 255.255.x.x

If these are good, then try

nslookup $you_isp_domain

and you should get its DNS ip address
If you see timeouts anywhere, then you have other issues than just 'dropping the connection'