install fails completely

I am installing ubuntu on a very old computer (600 Mhz, graphics card 6 Mb,...) but i have 4 Gb free space on my C drive (and a second drive of 70 Gb). i insterted the 7.10 cd, and he gives me the start/install ... screen, and i go for the start/install ubuntu button. then a box comes on the screen, with an orange bar who goes from the one side to the other, but then it goes wrong. the orange bar freezes abruptly (mostly in the middle of the screen) and then the screen becomes black. I have been waiting ( a whole night), but nothing changes.