Dual Boot Installation Question

I have read many tutorials regarding dual boot, but it's mostly about having 1 partition of OS (ex. windows) and the users have to create a new partition.

I'm really not familiar with those stuffs so I don't understand the tutorial that much to apply it to my case. Because I already have 2 partitions, The first one has 50G where my Windows OS is, and the other has 100G where my other stuff is (It has 50G free space left).

I'm really unsure how to apply what I see in the Tutorials (from youtube and google).

I'm pretty sure though, that there's an easy way to install my backtrack (I already burned it to a cd), because I already have a second partition it can use. I just don't know exactly how.

man, the only advice i can give you at the moment is DO NOT play with partitions unless you know what you're doing (which you've just admitted you don't know :) )
If you want to play with it anyway, then create third partition and install BT on it, but make sure you choose that third partition when going through installation process otherwise you will either wipe Windows or your data partition.

Each OS must have its own partition on a hard drive, you may try resizing the partion that you have space on to leave room for a third partition for backtrack. (google magic partition) you can also resize partitions in vista and 7. after you have some free space on the hard drive run install.sh from the live cd, and select 'use continuous free space' or Manual install=(add swap area and ext3 filesystem with / mount point. swap area doesnt need much space, 1000mb is fine and the ext3 should be as large as you want) and you should be fine, when it installs grub it should automatically put the windows boot loader in there for you.

Alright I was able to make a third partition, somehow. I played around with it and luckily I didn't mess it up.

So now I have:

1st partition - Windows XP
2nd partition - Some Craps
3rd partition - Empty

They're all at around 50GB.

So when I boot the CD, I'll choose Manual Install. Then right click > Edit the third partition. But I'm not sure what to do next. It makes me choose between "NTFS, Swap, ext, etc".

I would want to not seem like someone expecting to be spoonfed but I tried searching before I posted this, and also, I would usually try things first to see the result instead of asking people. But I really don't wanna risk messing up on this one.

You want to choose ext3 for your main partition, and add the '/' mount point. dont make it the full size of the remaining free space. leave about 1gb of free space. after thats done select the remaining 1gb of free space and make it a swap area. after this it will install and your done.

when partitioning (in Gparted?) avoid touching NTFS partitions as those are Windows partiions likely the third one you created is NTFS as well then watch out labels , i mean the partition names you can see them in ,,My Computer,, in XP.