Kindly advise me on this Memory Upgrade issue

Hello,
i need some advice and help i have a Intel Pentium P4 1.5 GHz processor desktop with one 256 Mb RAM of DDR266 type and i am planning to upgrade my system to a 1024Mb RAM with 2*512Mb RAM's. as i am need to practice & run Java Development applications like NetBeans,
with a web Serve (not for hosting -- like J2EE or other web servers) along with a database on the same machine.
On my current configuration the peak memory load including swap when i run these application goes up to some where around 800Mb+,making things slow down horriably . so someone kindly advise me if i can go for the upgrade of my RAM and can that help me improve the system
performance. kindly also advise me if there exists any performance factor in the ratio's between the size of my processor L2 Cache to the System RAM size. i also took a system HW report and have attached that down below here for the correct current configuration.
kindly advise me
cheer up
with regards
Madhu Sudhan

System Information Report
1/26/2006 6:06:35 AM

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Current General Information
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Product name Intel(R) Desktop Board D845GVAD2 based system
Board model Genuine Intel(R) D845GVAD2 system board

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Processor
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Processor Genuine Intel(R) Pentium(R) 4 Processor
Processor speed 1.50 GHz
Bus speed (FSB) 400 MHz
L1 cache Data Cache 8KB, Execution Trace Cache 12K Micro-ops
L2 cache Advanced Transfer Cache 256 KB
Form factor Socket 478
Stepping 10

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System
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Physical memory 256 MB RAM
Memory speed DDR266
Memory type DDR, Synchronous
Form factor DIMM
BIOS date 03/10/2003
BIOS size 512 KB
BIOS version P15 (LY84510A.86A.0038.P15.0303100232)

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Mother Board Additional Information
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Memory Module Requirements
Desktop Board D845GVAD2 supports system memory as defined below

Up to two 184-pin Double data rate (DDR) SDRAM Dual Inline Memory Modules with gold plated contactes. Supported Memory Configuration are:

--- DDR333: to run DDR333 memory at full speed requires a Intel Pentium 4 Processor with 533 Mhz front side bus (FSB). DDR333 memory will run only at DDR266 speeds when using a Processor with 400MHz FSB.

--- DDR266: requires an Intel Pentium 4 Procesor with 533/400 MHz FSB

--- DDR200: requires an Intel Pentium 4 processor with 400 MHz FSB

-Unbuffered and non-registered single or double-sided DIMMs
-Serial Presence Detect (SPD) memory only
-Non-ECC RAM(ECC memory will run in non-ECC mode)
-2.5v Memory