Im trying to do a basic thing, UDI Windows 7 install.

So I have created an MDT task Sequnece in SCCM 2012,

Boot Image, MDT and USMT (event thoght i not need it) where nade by The task sequnece

after Virtual PC it pops out a Command Prompt, then another windows asking for PC name, and if i give it any name and click next it just reboots and start from the begginign.

This is driving me mad now...

Windows Deployment Workbench was so stright forward, SCCM just to make a PXE bootable Vanila Windows 7 already took few days.

1) what couses the above issue ?

2) is there a good step by step deployment guide that works ? 

Im tring to deploy to a New PC (out of the box pc) / (VM for testing) so it would be in (All unknown Computers Collection)

Have you examined the smsts.log on the client? This is always the first place you should look for issues.

Based on the symptoms you describe, the boot image does not have the proper network drivers and thus cannot communicate with the site. There are other possibilities, but until you review the log file, all that can be done is guess work.