Hi biskit5674, and welcome to BleepingComputer.
In order to boot from a USB device your BIOS must have the option to boot from a USB device. If it does, then the USB device has to be the first device in the boot order in the BIOS.
There are several possible reasons for this NTLDR error.
Do you have a bootable CD in the optical drive when you try to boot.
If this file is corrupted, then you may need the installation disk to do a repair installation to correct this.
Can you boot into Safe Mode? If you can, then you will be able to use the other advance boot options. I would suggest trying the Last Known Good Configuration. Usually pressing F8 and holding it during the boot sequence will get you to the advance boot options.
You can also boot into Safe Mode and do a System Restore to a date prior to this problem.
Reason for edit, to add greeting.
Edited by dc3, 18 September 2010 - 11:19 AM.