Processor Upgrade for my Dell Optiplex 320

OptiPlex 320

General
ServiceTag	Service Tag removed per privacy policy >
Family Name	OptiPlex
Family Model	320
Windows Version	Microsoft Windows XP Professional
BIOS
Version	1.1.12
Vendor	Dell Inc.
Date	2009-06-17
Processor
Model	Intel(R) Pentium(R) D CPU 3.00GHz
Speed	3 Ghz
Hard Drive
Drive Size Free Space Utilized C: 74.5 Gb 33.24 Gb 55 %
CD/Optical Drives
Drive Type E: HUAWEI Mass Storage USB Device D: TSSTcorp DVD-ROM TS-H352C
Sound Card
Model	SoundMAX Integrated Digital HD Audio
Card Slots
Slot ID Designation Usage System Slot 0 SLOT1 In use System Slot 1 SLOT2 Available System Slot 2 SLOT3 Available
USB Controlers
Name Version Standard OpenHCD USB Host Controller USB Standard OpenHCD USB Host Controller USB Standard OpenHCD USB Host Controller USB Standard OpenHCD USB Host Controller USB Standard OpenHCD USB Host Controller USB Standard Enhanced PCI to USB Host Controller USB2
Video Adapters
Model Memory NVIDIA GeForce GTS 250 512 Mb
Memory
Total	2048 Mb
Available	67 %
Slot Size Speed Type Slot 1 2048 Mb 667 Mhz Unknown Slot 2 Empty
Available Slots	1

 

I recently, got a Dell Optiplex 320 Mini-Tower. I noticed that this one still needs improving so slap in a Palit GTS 250 E-Green (made modifications to make it fit) and replaced the memory with a Kingston ValueRAM DDR2-667 memory (1x2GB). Why not DDR2-800? I did use a Kingston ValueRAM DDR2-800 (KVR800D2N6/2G) memory but it won't boot. Last, a 600W PSU to accomodate my GTS 250 even if it is a E-Green version (E-Green  is "extreme power saving" says Palit).

I thought it was enough, sadly no. So bought an Intel Dual-Core E5200 (E7200 only 5% faster than E5200) to replaced the old Pentium D 925 and to match the FSB of 800. Here is my real problem started, it won't boot! No matter what I do it still won't. After Googling about Dell Optiplex 320 processor upgrade, I still can't find a real answer on WHAT IS BEST PROCESSOR I CAN BUY FOR MY OPTIPLEX 320. I don't like the stock Pentium D 925.

I have seen someone here posted that his Optiplex 320 runs on FSB 1066. He used an Intel Core2Duo E6700 with 1066 FSB? But why can't my Intel Dual-Core E5200 with just 800 FSB run/boot? If this E6700 is the only tested fastest processor to go with my Optiplex 320 then I will get one but only after I know what is the exact specification because Intel makes variation on a same processor model, that's a fact.

Kindly let me know if anyone knows a thing or two on how can I solve this.