I haven't been able to boot Ubuntu from USB on Dell Dimension C521.
The machine currently runs XP and I wanted to try out Ubuntu, in particular to assess the performance of flash video.
This means I need to load the nvidia drivers and the adobe flash package.
The Ubuntu live / install CD works, but you can't install the nvidia drivers without rebooting.
I had the same problem with a Linux Mint live CD (this has the adobe flash built in).
I then made a bootable USB memory stick holding the live Linux Mint. On another Dell machine this booted perfectly, but on the C521 it got ignored and it simply booted XP.
I transferred the Linux mint live CD to a hard disc with a USB connector and tried that, with exactly the same results - it was ignored,
I then tried connecting a 9.1 Ubuntu system disc via USB. This did get recognised, but the boot stopped within a mysterious grub text console (sh:grub), with no clue on how to proceed. Guessing, I tried typing 'boot', but the shell would say no kernel found. There was no 'kernel' command. Typing 'exit' booted me back to XP again. I tried this also with the XP internal O/S disc disabled via the BIOS - and got the same result.
Anyone got any ideas on how to do this?