Formating SLR SD Cards?

I just recentaly had put some Video (WMV) On my SD Card, The Problem is that i now can't get into my card after putting it on a different computer.
When I open it, it tells me to format it and when i do it says "Windows is Unable to Format this"
I tried formating the Sd Card with my Nikon D3100 and it said it's formating but nothing happened?
How do i fix this Please!

You can try this:
https://www.sdcard.org/downloads/formatter_3/

Go to google
type photo rescue

then buy a new card
format it before using it
the manual tells you to do this

Make sure you didn't move the write-protect tab on the SD card by mistake.

And when you say you put the card in a different computer, was it a Mac or Linux computer?

If so, did you possibly reformat the card using one of those computers. The Mac and Linux by default use different file systems, which are not recognized by either Windows or your camera, and often - Windows has a hard time reformatting something done on a Mac or Linux.

If that is the case, simply go back to the Mac or Linux computer, reformat the card in Fat32, which will allow your camera to access the card - then for giggles, reformat the card in the camera.

I guess your card has some kind of bug (might be FAT issue) which prevents windows to format it correctly.

First, try to copy another file to the card and check if it is working.
Than try to find a device that is capable to format it- card reader, another camera, etc.
Once you are succeeded, try to format the card again with your camera.