MT4G microsd hc card upgrade

MT4G came with 8 GB micro sd hc card partition as fat32 , a slower one(class 2).
with a faster one on hand(SDC4, class 4, higher number mean faster speed),
Partition backup with ghost32 render whole operation succeed.
Disk backup feature for some reason unknown, cause backup failure.
Setting: Asus EEEpc w/XP home, ghost32 portable