Welcome to DaniWeb.
>>Just built custom computer and i want to learn linux
Good luck! Come back in about 10 years and tell us how it went :)
Well, the best thing is to ease yourself into a new operating system, rather than jump in at the deep end. I use the Ubuntu distribution of Linux, and I have found it to be easy to install, use and modify, and I am not an IT geek by any means.
Check it out here: http://www.ubuntu.com
There are several versions, Ubuntu, Kubuntu, etc, and you can get Desktop or Server. Server is a bit frightening, for it gives you a simple command line interface - not for the uninitiated, so go for the Desktop version of Ubuntu which will give you a nice, useable Gnome desktop to work with.
Use the 32 bit version for starters, as the software support for it is better.
You can get plenty of help at the Ubuntu forums http://www.ubuntuforums.org and they are not going to laugh at you if you ask a simple "newbie" type of question.
So, download the desktop CD and do an install. You will probably find that you make the odd mistake or two in the installation. That is OK, you will learn from that.
I have to say that I have enjoyed my time using Ubuntu (since 2006). It is worth getting to know.
One word though. It is not Windows. If you are expecting an operating system to look like Windows, feel like Windows and run Windows software, then best stay with Windows. Windows won't run Linux software and Linux won't run Windows software (there is a way to run some Windows software, but not for you yet), the same as Macs don't run Windows software.
Linux is generally more secure, more robust than Windows, but it is not Windows. There are areas where it is far better than Windows, and there are areas where it is decidedly lacking, when compared with Windows.
Just get Ubuntu Desktop and have a go. I think you will find it is not as bad as some people think, and certainly won't take 10 years!!