Need help on installation

Need help on installation

I am booting my computer from a USB drive with Ubuntu 12.04. I clicked
"try on" logo at the first screen. It works just fine, but about a month
ago it didn't work this way. I used to get a blank screen with a message:
display at low range or something like that. After that I installed Ubuntu
13.04 the same way from a USB drive, but due to some problem I had to hard
shutdown my computer, and after that it wouldn't start again.
So now I am trying once again to install Ubuntu 12.04. Will the same
desktop appear when I completely install Ubuntu 12.04? Will all my data be
erased when I install Ubuntu 12.04 (because I am currently using Ubuntu
13.04)?