As an owner of 2 slim ps2's, Swap Magic, and KH2FM+, I can say that so far, all previous posts are either wrong or unhelpful.
Now to solve that problem!
First, You need to mod your ps2 to work with Swap Magic. The fat ps2 can be moded with the slide card, but unfortunately, it is useless for your slim ps2.
What you will want to do is block the sensors that stop your disc when you open the ps2. You can either buy some funny metal tools to do this, or you can do it for free with common house-hold items! (The second is much cheaper/faster/and fun, just don't be an idiot and ruin your ps2).
There are videos on youtube that show how to mod a slim ps2, that you can search for, but these require that you open your ps2 and void your warranty.
If the videos don't answer all your questions, go to afterdawn.com and search for 'tape and tissue mod' (that's what you do to mod the slim ps2).
Good luck, and happy moding!