What is 'd Maximum PhysicalMemory 4 WinXP? How can...

Question

Im workin with a DELL 690 Precision Workstation w/4GB DDR2 and 512MB PCIe video card, HDD 250x2 sata..... using XP platform i already used the 3GB switch Physical Address Extension.. What is d maximun DDR2 i can use w/XP? how can i speed up my 3DMaxrendering? what are d correct Processor Settings from d BIOS 2speed me up???
Pls. help me out guyz....