dear all
i am new here and i would like to start learn unix/linux first i need to know how and where i can install linux on my PC

Thanks

Download Ubuntu | Ubuntu

I recommend Ubuntu. It's the distro I use, and it's easy if you're new to Linux.

If you don't know how to use the link I sent you:

1. Download a disc image (file ending in .iso)
2. Use a CD burning program to make a CD from that disc image
3. Put that CD in the machine you want to install on and reboot
(if the installer doesn't start, figure out what key to press on boot to enter your BIOS and tell it to boot from the CD-ROM)