我想加ram把電腦升級,help!!

我的電腦是幾年前自己找人裝的,但是近來玩新games時,經常lag和virtual memory不足.我想幫電腦加ram,請各位俾d意見.例如咩牌子,種類....等等

我電腦的資料係:

Motherboard:
Motherboard Name:
Intel Brownsville 2 D845GEBV2 (6 PCI, 1 AGP, 2DIMM, Audio, Video)

SPD Memory Modules:
DIMM1,256 MB PC2100 DDR SDRAM (2.5-3-3-6 @ 133 MHz) (2.0-2-2-5 @ 100 MHz)

CPU Properties:
CPU Type:Intel Pentium 4
CPU Alias,Northwood
CPUID CPU Name:Intel(R) Pentium(R) 4 CPU 2.00GHz
CPUID Revision,00000F24h

Thank you!!