Finder not recognizing Sandisk USB

I think you mean drive (hardware) vs. driver (software to run a device).

Are you plugging this into the computer directly? Some USB devices draw more power than the computer can supply and require a separate powered hub.

If it's brand new it may need partitioning and formatting. Most come ready for PCs and are not in 100% ready condition for Macs, though usually they do at least show up on the desktop.

When you plug it in does it appear on your desktop as a drive? How about in the sidepanel in Finder? What about if you open Disk Utility, does it show there?

Where are you plugging this into your computer? Have you tried other USB ports?

Do you have a powered USB hub into which you can plug it versus plugging it directly into your computer?

Are you sure it even works? Have you tried it in another computer?

I'm experiencing the same thing. I have a (brand new) TASCAM DR-07 audio recorder (very nice device). I can connect it and use it w/o trouble under OS10.4.11 on a G4 iBook. When I attempt the same on our brand new mini (OSX 10.5.6), it won't show in the finder. It shows under the System Profiler as USB device. The DR-07 also indicated that it is "connected". Same thing with a friend's iMac w/ OSX 10.5.6.

If I remove the SD chip from the DR-07 and use a "Core Micro" or Verbatim USB card reader (on the same USB port), the SD chip shows up fine in the finder.

This problem has started appearing rather frequently in the forums.
(Did something happen in the upgrade to 10.5.6?)

Here's how I fixed it:

Open Finder->Preferences
Select the "Sidebar" panel configuration at the top of the Finder Preferences box.

Under the list of "DEVICES" see that "External Drive" has a box next to
it. Chances are, it is not "checked" on your machine, but instead has either
a minus sign "-" or an empty box. Click on the little box next to
"External Disk" until it shows a check mark. Now your USB drive should appear.

Re the suggestion from BigNComputing that "external drive" is not selected, I'm afraid that this isn't the problem in my case. "External drive" is, and always was selected (with a full check-mark).