I've seen similar, but not exactly the same question here, so here goes...I have a Dell Inspiron 8100 with 256MB ram and 10G HD. I am using Puppy with live CD and made a couple of different USB thumb drive installs with the intention of using the USB only - no CD. The problem is that I can't seem to boot up from the USB on my computer. No problems booting up on other, newer computers. I think it's a BIOS problem. I've tried formatting the USB thumb drive as a floppy, and I've made the HDD the last thing to check for boot on my computer, but to no avail.
Any suggestions?

If the same USB stick boots on some PC's but not others - then it's definitely a BIOS problem.

SUGGESTION:
1. Insert the USB *first* (before you power-on).
Some (brain-damaged!) BIOS's "lose" boot-from-usb settings if they don't see the USB at power-up

2. Upon booting, go into the BIOS setup *immediately*.
EXPLICITY set "usb" in your boot options, and make sure it's at the TOP of the list.
Explicitly SAVE your settings.

3. With luck, you should be able to boot from USB.

My USB-sticks are all seen as harddisks in my BIOS. Some BIOSes allow to change the order of every type of drives (CD, HDD, USB) specifically, so try if you can find the USB in your BIOS under "HDD Priority" or similar.
Sadly, and this may be true for you, some older BIOSes can't boot from USB at all.

You have hit the nail on the head. My BIOS does not seem to support USB boot-up. I tried formatting the stick to appear to be a floppy, but still no luck.