I know I'm stating the obvious, but for those who have just entered the thread and maybe have skipped to the end, here is my diagnosis:
It appears as though the ID3 tags on the MP3 files on the PC have been altered.
If the files on your Archos do not have this problem, then you might be able to copy the files off of your Archos player back to the PC and it will likely solve the issue.
*MAKE A BACKUP OF YOUR MUSIC COLLECTION BEFORE YOU DO THIS*
If you don't backup and this doesn't work, you might be SOL and have to re-download...err...re-rip/purchase your songs from IsoHunt...i mean CDs/iTunes. It might also leave you where you are now, but it's not certain.
To do this, on your Archos, open Settings and click system. change the USB mode from media device to hard drive, exit back to the main screen, and plug your Archos in. Now it will show up as a hard drive and you can find your music files and copy them back to your hard drive. Make sure you say "yes to all" if it asks about overwriting.
If this doesn't work, go to the website below and find a program that you understand that will allow you to re-work your ID3 tags and such. WMP has this option built-in but it can be slow if you don't know your way around it. right click on a song and hit properties, or select a large number of songs (IE: an album) and hit properties. Be careful with this, as you can change the title of every track on the album to the same song, and it might be a pain to undo.
http://www.download.com/3120-20_4-0.htm ... eSize=&ca=
EDIT: One of the programs at that URL might be able to convert the filename (listed in windows explorer) into the title from the ID3 tag. I've used a similar program before, but it's been a long time and I'm having trouble finding it. I will post a reply if I find something useful.