Basically what shadows1234 said above.
The 4 GB DIMM may not be compatible with the G41t-M7 motherboard, or the DIMM is faulty, or maybe the DIMM is incompatible and faulty.
Try the DIMM in another computer (friend, neighbor etc).
It is recommended that memory compatibility be checked before purchasing memory. Best source of compatibility check is to use memory manufacturer memory compatibility (configurator) function which is available at most major memory manufacturer websites.
Note that the motherboard basically supports up to 1066 MHz DIMM's. DIMM's with faster speeds will (or should) be automatically down-clocked to run no faster than about 1066 (or about 1200 MHz with 1066 MHz FSB CPU).