I know i'm supposed to go outside throughthe basement door after pounding those two pillars. But i keep looking for the hole i'm supposed to jump into and activate the swtich. I've searched everywhere but cant find it. Please help.

Well, first, wrong cap switch. The one you're heading for is the Vanish Cap Switch course. When you go through the door and find yourself in the now drained moat run to Mario's right and follow to the end. Near here is some water and the waterfall. The hole is in the ground around here.

U mean a hole in the water. I tried getting in but its blocked

When you drain the moat the hole should be out of the water and uncovered. Don't go jumping into the water as that is the exit of the course, and it is impossible to get in that way.

I dont see any hole. I've gone outside the castle through the back door and searched all round but i cant find any hole except that in the water but then it doesnt have any exit. I'm playing on the nintendo ds. I'm wondering if its different.

XD lol, you should have said it was the DS version.

There's a black brick stuck in the ground, isn't there? You have to unlock Wario first and switch to him, as only he can smash that brick and allow access to the hole.

It's not a cap switch course though. They changed things in the DS and now there is only the one cap switch course (the one accessed from the main hall). This course now serves as a mini world to get some castle stars.

Now i understand cos i've just ben strolling running and walking around looking for the whole. Yeah, i got the name all wrong. I have to go look for wario then. Thanks.