Above is for reference only
"Which board D865GBF can I replace with, for the latest upgrades?
Speed, and everything?"
If I take your question literally;..............None.
The latest upgrades for Intel is their Core i processor line-up, based on the Sandy Bridge micro-architecture, and Ivy Bridge 22nm manufacturing process,http://en.wikipedia.org/wiki/Ivy_Bridge_%28microarchitecture%29
[ Intel Core i was first based on the Nehalem micro-architecture,http://en.wikipedia.org/wiki/Nehalem_%28microarchitecture%29http://www.hardwaresecrets.com/article/535
The Processor socket isn't even the same.
The motherboard chipset is of a different architecture.
The ram memory slots are DDR3 Sdram.
This means NOTHING from your old computer setup will work.
Doubt the Power Supply even has enough Wattage, or voltage on the 12 Volt power rail.
Means you need;
1) An Intel Core i processor
2) Motherboard that supports that Intel Core i processor
3) Ram Memory that is supported
4) Power Supply
In otherwords a new computer.
Upgrade with the hardware components you have?
The Intel D865GBF motherboard chipset is an Intel 865G,http://en.wikipedia.org/wiki/List_of_intel_chipsets#Pentium_4_chipsets
Scroll down to 865G in the left column. (Springdale)
A) Processor support:
Intel Celeron, Intel Celeron D, Intel Pentium 4, and Intel Pentium Extreme Edition.
Has to use 400MegaHertz, OR 533MHz, OR 800MHz; -> FSB.
(Front Side Bus)
Has to fit in a Socket 478 processor socket,http://en.wikipedia.org/wiki/Socket_478
B) Ram Memory support:
DDR Sdram at either 266MegaHertz, OR 333MHz, OR 400MHz.
Ram memory TYPICALLY, operates at HALF of the processor's Front Side Bus.
The graphics expansion slot is an AGP. Uses AGP 8X graphics cards,http://en.wikipedia.org/wiki/AGP
If you are using an IDE (PATA) harddrive, and not a SATA harddrive; there is another problem.
E) Optical Drive: (CD/DVD drive)
Can be IDE (PATA) optical drive/s, but newer mobo's are going to SATA.
Forget about it. By the time you upgrade you could buy a budget computer, that uses at least an Intel dual core processor, and DDR2 Sdram ram memory.
Maybe Intel Core i processor, and DDR3 Sdram ram memory.
Plus there is one more factor:
The Operating System
When Windows is put on a computer it assigns hash values, to certain major hardware components.
B) Motherboard chipset, and BIOS program. (To include version and date)
D) Graphics chipset
Change any TWO of these components, and Windows will 'think' it is being stolen. Taken off of that harddrive, and put on another computer.
This = NO.
Microsoft User's License states, "One GENUINE copy of Windows per ONE computer"
(Microsoft makes one Master disk of the Operating System.
From it all GENUINE copies are made, and sold to the consumer )
You MAY be lucky, and the Windows activation screen will come up.
Then you just re-activate. (Not Register; Activate)
You also MAY not.
Means you will need the Restoration Disk for YOUR computer; or a new Genuine copy of Windows.
DO I sound discouraging? Sorry. Don't mean to be.
Just don't want you to waste your hard earned money, and also wind up with a dud for a computer.
For additional questions please post in a Comment.