USB Flash Disk Boot Issues with Optiplex 740

Has anyone been able to successfully boot from a USB drive with an Optiplex 740? I been able to do so with a Dimension 9200, but NOT the Optiplex 740.

To test booting, I format the USB drive with the XP embedded tool UFDPREP.EXE in FAT32 format and then copy NTLDR and NTDETECT.COM to the formated USB drive.

WITH DIMENSION 9200 (works):
I Plug in the USB and boot into the BIOS manager. The USB drive shows up as a USB-ZIP drive. I choose to boot from the device and on boot, NTLDR runs and lets me know that all of Windows is not installed (I only have NTLDR and NTDETECT.COM on the USB Flash).

WITH OPTIPLEX 740 (does not work):
I Plug in the USB and boot into the BIOS manager. The USB drive shows up as a USB-ZIP drive. I choose to boot from the device and on boot, I receive an "Invalid system disk" error from the bios. NTLDR never runs!


Both USB FLash:
- SanDisk Cruser 2GB U3
- PNY 1GB Attache (non U3)

Work with the Dimension, but not the Optiplex. Any suggestions or lists of compatible USB Flash drives with the Optiplex would be very helpful. Thanks.