problem loading animation

Hi,

got an old imac as a present. installed ubuntu fresh by erasing the HD. new to Linux. so, besides the wifi problem that i may address later, i found in the "Help" section, as i try to e.g. watch the animation about getting started, launch application, it stops after a couple of seconds, the pointer (mouse cursor) stays with the hand sign, and thereafter comes the message "ubuntu encountered an internal error...send report...".

I'm asking this specialy since I'm afraid i might have a hw problem. See, i just wanted a working computer. with apple original os many problems regarding animation and video plus not loading some pages at all (including java.com - i intend to program again after couple of years no activity and no computer) occurred that i switched to linux. i couldnt dl ff, adobe flash also wouldnt install...for example.
the apple is from about 2010. also i never used apple.

p.s. also i checked if i can play a dvd movie and as i click on open with videos, comes the msg "unable to play the file, dvd source is required to play the file, but not installed.

thanks in advance.