Multiple Hard Drive Help!

Okay. So I thought all you had to do for multiple hard drives is make sure they are formatted then plug in the sata and the power cable .. But I am finding out it is much more complicated then that.

I have 3 hard drives in my computer currently. The one is my main one that I started with, using vista with all my data on it. The other 2 are plugged in, the sata cables are plugged into the motherboard right next to the main hard drive.

-In my computer its showing floppy disk drive A: and I dont have a floppy drive.

I have heard that I need to set some kind of jumper or something idk, i have no idea about jumpers nor can I find any information that will help me.

Something about 1 on the master drive and the rest have to be set as slave. No idea how to do any of that or what a jumper even is.

2 hard drives are the same, the main one is different.
2 80gb Hard drives
250gb hard drive

I also have 1TB USB external hard drive .. I just got it and plugged it in and it showed and everything and I put some data on it then I remember I somehow disabled it or something and now it wont show in my computer but itll show in device manager. People are saying its broken, I dont see that being possible since I havent moved it since I took it out of the box.

I would like to know what would be the best thing for me to do with all of these hard drives, and how to do it.

I have tried to google this and have spent hours reading but I just dont understand it ..