Ok. I will tell you my current set up before I start asking questions.

Windows XP Media Center (SP3 + all updates)
Motherboard - Dell 0FJ030 (BIOS - A05 date: 05/30/2006)
Processor - Pentium D 940 @ 3.2ghz
Memory RAM - 4 Gb DDR2 @ 266.0 MHz (no name brand? It's all black)
Video Card - BFG Nvidia GeForce 9800 GT Eco Intelligence Edition
PSU - Dell PSU @ ???. It was able to run my old BFG 8800 GT Over Clocked edition just fine. So I'm guessing it's between 450watts and 500?)
HDD - Western Digital Caviar 320gb @ 7,200 RPM
Sound Card - Soundblaster Xifi
-------------------------------------------------------------------------

I had asked for a new CPU for x-mas and it has already been ordered for me. What I am getting is an Intel Core 2 Quad Q9550 Yorkfield 2.83GHz 12MB L2 Cache LGA 775 95W Quad-Core.

Question a):In certain games, which are older and only use a single core, would I feel any performance drop? b) If so, can I overclock this Quad Core (2.8 ghz) back to my old Pentium D CPU setting which was 3.2ghz only using air? (the CPU is also shipping with some Arctic Silver 5 Thermal Compound, and the CPU cooler in my case seems to be huge and works fine).

-------------------------------------------------------------------------

I was also wondering if these parts that I am buying in the near future to upgrade my old PC would conflict with my motherboard or any other parts/software? I tried to use google, but not much results turn up.

so here is my upgrade list that I may purchase , and I would appreciate any helpful input.

1. G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1200 (PC2 9600) Dual Channel Kit

2. CORSAIR CMPSU-650TX 650Watt

3. (x 2 in RAID0) Western Digital VelociRaptor 300GB 10000 RPM 16MB Cache SATA 3.0Gb/s 3.5"

4. EVGA GeForce GTX 460 Superclocked 1GB 256-bit GDDR5 PCI Express 2.0 x16

5. Windows 7 Home Premium 64bit ( Or whatever is the equivalent of Media Center for XP)

--------------------------------------------------------------------------

Thank you very much for any who respond with great advice.