The SD card slot on the Acer w500 tablets has been known to have an issue where you are unable to insert the SD card into it.
The cause for the SD card not being able to slid into the Acer w500 tablet is that there is a plastic insert that can slide in and out. This has a sticker on it that lists the Windows License Key for that tablet. The top part of this insert can get bent down and not allow the SD card to slide in.
You can remove this insert by sticking a razor blade, pen tip or something else small like that into the top of the insert. There are 2 small holes on the top of the insert where the utensil can go. pull straight up to reveal the entire insert and then with a firm grip, you can pull the entire insert out of the tablet.
We suggest that you keep this insert in your files in case you ever need to restore Windows on that tablet.