Dear member of SanDisk Community, welcome.
Friend, try with another card, to delimit the problem.
1- Please, clean the pins of the card, and device slot, with isopropyl alcohol (or if not, medicinal).
2- Test your card, microSDHC of 8 GB, in a other laptops, directly to its port-card.
3- If still bad, in Start / My Computer , on the card icon, click the right mouse button, and then click in Properties/Tools/Error Checking and Repair.
4- If still bad, back up your data and try formatting with (free): USB Flash SD Formatter 4.00, http://filecloud.io/jqtu1byc
5- If still bad, or gives “write protected”, is dead, can return it.
6- If the above steps have not solved the problem, please back up your data, and contact SanDisk Technical Support, who will replace the device, if it’s authentic and within warranty.
SanDisk Technical Support: http://www.sandisk.com/about-sandisk/contact-us/
Luck, and then you tell us, what happened, please.
Regards, Alfred. (Google translated)