I can boot from USB a installation of Windows 7, but I can't do this with Ubuntu or XBMC live

I'm using a old pc with Intel Pentium 4, 1gb ram, 200gb HD
All this night I tried to boot Ubuntu from USB...
I can do this with Windows 7 normally

I tried first using Startup Disk Creator, but freezes.
I tried using UNetbootin, freezes too, choosing any option
I tried CD, but continues the boot of windows the a I have installed
So, I tried booting a Easeus Partition from boot, and work, and I format my disks normally
But anyway, when I boot Ubuntu, don't work...

I don't know what I do to install Ubuntu in my PC, I need help...

Thanks

P.S.: Sorry my english, I'm from Brazil

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I'll explain using my language and translated in Google Translate
Then again explaining ...
I am able to boot the Windows installation via USB, works perfectly, but when I do this using the Ubuntu image, it simply does not start.

I followed all the steps from the Ubuntu site itself to make a bootable usb using the Startup Disk Creator program, I create perfectly and when I boot, just hangs/freezes on a purple screen.
So I tried using UNetbootin, I create perfectly on usb but when I boot hangs/freezes on the choice of options.
So I finally put the image on a CD of Ubuntu, and also does not work ...

I'm not having trouble creating a bootable USB, but the problem is own boot screen.
I chose the option to boot from USB, it recognizes and simply does not work.

I was able to install Ubuntu on my Sony Vaio notebook, but this PC I can not in any way.

I can install windows via usb as many times as I want, but Ubuntu is not working.

P.S.: The same thing happens with the XBMC live