My SD card reader on my T500 works only with SD cards. When I put it any SDHC card, it askes me to format it. The card reads perfectly fine on Linux and with a USB Flash Drive adapter for it but why doesn't it work directly? It is because I need to update it?
Check to ensure the drivers are fully installed. Open the Device Manager and select option to update the drivers, and indicate the source location as the SDMMC folder that the extractor created when it initially unpacked.
Additionally, some OS fixes could apply such as this one for XP users: