It is possible with certain front end platforms. With the platform I use you can setup a dummy account that mimics a second account. I have a few customers that use one account to trade longer term strategies and the dummy account to trade short term. Mind you that both clear to the same...
One of the best traders I know, trades off a netbook plugged into a monitor. He uses Xtrader(TT). He says he has never had an issue. If all you run on the computer is your trading software and nothing else, you won't need a big rig. Throw your charts on another computer.