I recently purchased a Sonx XPLOD CDX-GT61UI. I bought an IBM Travelstar 100gb external USB hard drive on ebay to use with this unit. After 6 hours of hair pulling, I said F* it, and put it away. Then I called Sony tech support and I stumped them. They told me the drive was not DRM compliant....FUNNY!....and so for them. THEN I started to look at the drive from a partition view and GOT IT!!!!. These Sony head units DO NOT recognize NTFS. I re-formatted FAT 32 and it worked fine. Load time for approx 13gb is slow but you only have to do that unless you unplug the drive from the head unit. Sound quality through USB is superb. AM/FM tuner is weak in this unit but who uses those anymore.
Just thought I'd post this solution so the readers of this forum can use this info and it to show on google because there's NADA on this issue on the web.