File Transfer to ext USB 3 Drive?

Getting ready for the time I'll have my new iMac sitting on my desk, I planned to keep the bulk of my work files on a 500Gb USB 3 Toshiba on sale at BestBuy. ($35),

The drive is formatted for Windows. My present mac is a G4, running OS 10.5.
The new ext. HD is powered through the bus, so I plugged into one of my USB 2 ports. The power light on the drive came on.

But when I try to drag and drop folder so these files (all Jpegs and RAW photo images), I get an error message saying 'File Names Are Too Long". They won't write to the drive.

The drive was reformatted to Hfs w/ Journaling. What could be wrong?
(can't use Migration Assistant without Firewire Cabling)

Problem solved. My initial tries at formatting were with the Ext HD plugged into my G4 mac. I employed Disk Utility, and tried both the ERASE function and FIRST AID. Neither worked.

Bear in mind that the HD cable is USB 3, while the ports on my old Mac are USB 1 & 2.

No luck. So I next attached the drive thru the USB 3 port on my wife's brand new MBP running OS 10.7. That made a difference. Bear in mind that on both computers an orange disk icon appeared for after formatting.

I then did a drag-and-drop of two DVD's I had burned with the 7Gb of photo files in two separate folders. That wasn't as speedy as I expected. Probably due to the clunky read speed of the superdrive.