Does anyone do this? Is it possible to do it with
2gb ram
2.2 ghz
intel core duo 7500+
?

i do it

So can you tell me how to do it and if my computer is able to?

Make sure its window mode and open up two of them...? Thats what I do and it works out fine.

Your RAM sounds kind of low. Your graphics card (which you didn't list) plays a big role in this also.
On my old computer with 1 GB RAM and onboard graphics, regular play on medium settings was fine, but dual clienting was impossible.

Technically any computer with any specs can run more than 1 client... However you need really good specs to multi client and maintain a playable FPS.

I have Nvidia Quadro 140m

i dual client all the time, i have
3gb ram
nvidia GeForce 9500GT 1gb ddr2 vidram
intel dual core some shit.. 2.67ghz

you should be fine i think

I installed Windows 7 and my computer is a lot faster after
deleting the stuff. I am able to Dual Client now
But is Dual clienting not allowed? And if i get caught will i get
banned?

you won't get caught. it probably isn't allowed.. but almost everyone who can do it does it. nothing better then making a new character and using your Rm to buff it, instead of back in the day having to ask for buffs haha

Yea i know. I had to use two computers until i found out how to do this.