Do you guys think I will be able to try Windows 8 with this specs: Emachines M5312 1.8ghz processor 512 or 768of ram 320gb hdd running on windows xp.
Not according to the system requirements - http://windows.microsoft.com/systemrequirements/?SignedIn=1
There are many different distributions of Linux, but I would go with Ubuntu. All the help you'll need is here - http://www.ubuntu.com/