Installing Ubuntu on a new computer.

I'm trying to install Ubuntu on a friend's computer running Windows 7. I downloaded the most-recent .img from the Ubuntu site, mounted it with DaemonTools, and started the normal installation method by running it from the CD and asking it to restart the computer by itself. The installation seemed to go successfully until the screen said something about "kernel panic" and just halted. On subsequent restarts, I am able to load Ubuntu as per normal (choosing between Windows and Ubuntu right at the start of the boot-up), but after spending a few minutes loading I'm just left with a screen that says:

BusyBox v1.18.5 (Ubuntu 1:1.18.5-1ubuntu4) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs) Unable to find a medium containing a live file system.

Before that comes up I'm given five seconds to press ESC and choose five options:

Normal Mode
Safe Graphic Mode
ACPI workarounds
Verbose Mode
Demo Mode

Any ideas as to what went wrong and what I should do to get Ubuntu working? I still haven't created a partition (I went the Windows/Ubuntu partition route); so would it make more sense to just trash what I've done so far and start over, or is there a way I can work it out from here?

Thanks!
-Dylan