Computers won't read this micro SD...

Hello. I have this micro SD with 512 MB on it, but the computers in my house won’t read it. I have an adapter, of course. I also have a micro SDHC with 8 GB that run perfectly fine on the computers. The 512 MB card shows up on the phone it came from, but that’s it.

Does anybody know how to solve this?

Can anyone figure out this problem and find a solution for it? If you need more info, I’ll do my best to provide it.