Maxium Upgrade for Inspiron 530S(Desktop)

Hi. I have a DELL computer Inspiron 530S. What would be the maxium upgrade for the hardwares? (rams, cpus, graphic cards)

My Configuration now:

Computer Model: Dell Inspiron 530s

OS: Microsoft Windows 7 Ultimate  (32位)

CPU  Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz(3000 Mhz)

Mother board: Dell 0RY007

Ram: 3.00 GB (PC2-6400 DDR2 SDRAM 800MHz) (2.00GB+1.00GB)

Harddisk 500 GB (ST3500630AS ATA Device)

Graphic Card: ATI Radeon HD 2400 PRO (256MB)

Monitor: DELL SP2208WFP 59Hz

Audio: Realtek 888 High Definition Audio

Internet: Intel(R) 82562V-2 10/100 Network Connection