presario 900 XP SP2 do not recognize DDR 400

I have upgrade my presario 900 with apacer ddr400, but , it doesnt able to be identified by the system....i have scan the system using cpuz and the memory ddr 400 is detected....the question is why the system only show 240MB of ram......

Scan my presario with PC WizaRD 2007, the data:

General Information :
U5 (Bank 0 ) : 256 MB - DIMM

1)Information SPD EEPROM (U5) :
Manufacturer : Nanya Technology
Part Number : NT256D64SH8C0GM-6K
Serial Number : 84720797
Type : DDR-SDRAM PC-2700 (166 MHz) - [DDR-333]
Size : 256 MB (2 rows, 4 banks)
Module Buffered : No
Module Registered : No
Module EPP : No
Width : 64-bit
Error Correction Capability : No
Max. Burst Length : 8
Refresh : Reduced (.5x)7.8 µs, Self Refresh
Voltage : SSTL 2.5v
Prefetch Buffer : 2-bit
Manufacture : Week 9 of 2006
Supported Frequencies : 133 MHz, 166 MHz
CAS Latency (tCL) : 2 clocks @133 MHz, 2.5 clocks @166 MHz
RAS to CAS (tRCD) : 3 clocks @133 MHz, 3 clocks @166 MHz
RAS Precharge (tRP) : 3 clocks @133 MHz, 3 clocks @166 MHz
Cycle Time (tRAS) : 6 clocks @133 MHz, 7 clocks @166 MHz

2)Information SPD EEPROM (U6) :
Manufacturer : Apacer Technology
Part Number : 77.G1737.AR0
Serial Number : 02308105
Type : DDR-SDRAM PC-3200 (200 MHz) - [DDR-400]
Size : 512 MB (1 rows, 4 banks)
Module Buffered : No
Module Registered : No
Module EPP : No
Width : 64-bit
Error Correction Capability : No
Max. Burst Length : 8
Refresh : Reduced (.5x)7.8 µs, Self Refresh
Voltage : SSTL 2.5v
Prefetch Buffer : 2-bit
Manufacture : Week 0 of 2000
Supported Frequencies : 133 MHz, 166 MHz, 200 MHz
CAS Latency (tCL) : 2 clocks @133 MHz, 2.5 clocks @166 MHz, 3 clocks @200 MHz
RAS to CAS (tRCD) : 3 clocks @133 MHz, 3 clocks @166 MHz, 4 clocks @200 MHz
RAS Precharge (tRP) : 3 clocks @133 MHz, 3 clocks @166 MHz, 4 clocks @200 MHz
Cycle Time (tRAS) : 6 clocks @133 MHz, 7 clocks @166 MHz, 8 clocks @200 MHz

Memory Controller Information :
Memory Controller : System Memory
Location : Mainboard
Error Correction Capability : No
Number of connectors : 2
Max. Module Size : 1024 KB

help!!