i meet some problem with my seagate 160GB + CM Xcraft250L USB+eSATA

when i use it with Y USB cable + eSATA, it seems not enough power, coz the window only detect 1 partition (got 2 partition inside) and it is not usable (can see but canot use)

but when i use the Y USB + USB data transfer it seems ok, but after transfering file for around 8mins the window show me "file transfer failed".....

May i know why this problem occur, izzit the HDD or the casing too power hungry?
anyway to solve it?