This is what worked for me on 2007/10/15. Your experience may vary.

Before you do this, back up any files from the iRiver you want to keep. This procedure deletes all music and data currently on the the device.

1. I went to the iriver.com web site, to Support->Download
2. I used the site's menus to find the firmware upgrader for the T30. I knew my T30 had the "MTP" firmware preinstalled (this is the case if your T30 came with a Windows Media Player 10 disk). So, I followed the "[MTP] T30 Firmware Upgrade V1.71" link, and downloaded that .zip file.
3. In Windows XP, I ran the .exe file contained within the zip, and followed the instructions for connecting and disconnecting the iRiver. (However, I waited until the iRiver's little screen stopped saying it was transferring data before I unplugged it.)
4. The iRiver turned itself back on with a message indicating there was a firmware upgrade happening. I think it took about a minute before it turned itself off again.
5. I ran the .exe again, plugged in the iRiver as instructed. However, this time, there was an additional button available for MTP <-> UMS conversion. I pressed it.
6. I got warnings saying that if I continued with the conversion to UMS, I wouldn't be able to use Windows Media Player with the device anymore. I continued with no regrets. (Even in Windows, I never used WMP to access it. I either used plain old Windows Explorer (mainly for dropping .ogg files in the "Data" section, the only way I could use .ogg files with it) or Media Monkey.) Some other warnings popped up that I didn't care about.
7. Once again, when the upgrader program told me to unplug the iRiver, I waited till the iRiver thought the transfer was done before I unplugged it.
8. The iRiver turned itself off and back on again, and had a little message on its screen saying a firmware upgrade was happening. It might have been like that for a minute or two.
9. After it had been off for a while, I manually turned it back on. It briefly flashed something about the upgrade, and then indicated that there was no music file found. (All files on it had been deleted, as the upgrade program had warned.)
10. I turned it off, and went to my other PC which was already booted into Linux. I connected it via the USB cable, and turned the iRiver on.
11. Within moments, a nautilus window opened showing me the contents of the iRiver just like it was an ordinary file system. I created a folder. I dragged and dropped an ogg file. I was pleased to find it worked just fine.

my home page