Datel's software doesn't work with many other flashdrives other than their own. They want you to use theirs, so they don't strive to make their software work with other brands of drives. If you want to use your own flashdrive, Code Breaker is what you want, as they try to make it compatible with as many brands and models as possible, since they don't provide you with a drive with their product.
My PlayStation2 HDD guide.
NTSC J SCPH 30000 with HDD and PSBBN 0.32
NTSC U/C SCPH 30001R Astral Blue LE PS2
Final Fantasy XI status:
Server - Ragnarok, Race - Mithra, Jobs - BLM 72 WHM 51 SCH 39 SMN 25, Nationality - Windurst, Name - Bungiefan