SD card no longer working correct in PC

Well, the memory card used to work just fine. I was able to plug it in via USB and it would read and write at my lesiure and then put it back in my phone and everything worked great. Then my PC no longer reads the card correct. When I put it in, it tells me it needs to format the card. I allow it to format and it never completes, just errors out with unable to complete format. I can use another computer just fine. So I am not sure what I need to do to make this work on this PC again. It is a windows vista system.