Cant boot with ubuntu usb stick

I have this problem with me when i try to boot with my USB stick in dell laptop i can boot. I have used unetbootin to install ubuntu 8.04 live with an ISO that i have downloaded from official ubuntu site. But i can boot with my desktop computer why is it so?
anyone experienced this before?

The only thing comes to my mind is may be your dell laptop lacks the USB drivers thats why the USB stick is not being recognised & you cant boot with your Ubuntu USB Stick!

I recomment you to go through this once again!