Probably the easiest way to "modify" your slimline PS2 (aka, "PStwo") is by using tape and tissue.

You'll have to open up your PStwo and void your warranty, but otherwise, there are no cons to this method -- It's simple, and most importantly, it's free!

The PStwo has two tabs, one in the lower right above the power button (point A), and one in the upper left below the lid hinge (point C).
As long as both tabs are depressed, the PStwo will think the lid is closed. This is necessary for swapping out backups/homebrew apps
with the Swap Magic discs.

1) Point A is externally accessible through the hole which a lid tab usually goes through.

2) Point C can only be easily accessed by opening the PStwo case.

3) Point B, the disc brake, can be ignored for all intensive purposes.

The very first thing you'll have to do is remove the PStwo case by unscrewing the six screws on the bottom. If you've got a v13 or v14 slimline, the warranty sticker will be covering one of these screws; you'll have to remove it. A word of caution: be careful and don't use brute force when taking off the cover, or you might damage the power ribbon.

The far sensor tab is what we're interested in.	A closer look at the far sensor, which needs to be taped down.

Up close and personal.	Time to tape down the sensor tab with duct tape or another heavy adhesive material. Don't be afraid to use more than one layer.

Put your PStwo cover back on. Now we'll deal with the second of the two sensor tabs.

You can roll a square of tissue about 1cm X 1cm into a tissue ball.		Push it into the sensor hole.	Voila! You're done. Time to play your Swap Magic discs!

All backups, CD or DVD, should work fine if you have the Swap Magic 3.3/3.6 set. There is a small handful of games (roughly 3-4%)
which may not work with a straight swap, however. A compatibility list and solutions for "problem games" can be found here.

Swap Magic 2.0 users should look to this site for compatibility issues.