Nikon D3100 usb mount not working on Vista?

I just bought a new 16gb SD card for my Nikon and none of my readers can read it (except my camera) so I plugged my camera to my pc and it won't detect it (I think it has something to do with the file system on the card). Can anyone help?

Format it in the camera first

I agree, have you formatted the card in the camera? If not do that now because it won't work correctly until you do.

By "readers" does that mean you have a usb card reader? If not I'd get one. They're not expensive and are available where ever cameras are sold. I've been using them for years on both XP and Vista.

It's a SDHC card which you have, I know this because it's larger than 2GB

If you are buying a card reader, make sure that is capable of reading SDHC cards, a "standard" SD card reader ( for cards 2GB or lower ) will not read your 16GB… I suspect that's the problem with readers you've already tried.

… And format the card in your camera as has been suggested.
Make sure you save any photos on the card to your PC first, ***and double check*** as formatting completely wipes the card.