Dual Core procs are amazing at the least. For example you can run many background programs like PSCS2, Run virus scans, Burn DVDs, etc. while playing your favorite games with out the slightest pinch of lag (Also known as multitasking)
Lets start off with the Proc(processor):
Right now there are 2 companies that make procs, Intel and AMD.
Single-Core Procs are underlined, while Dual-Cores are Bolded
Starting off with intel:
Intels procs are divided into many subcategories(its a pain ): Celeron D, Celeron M, Core-Duo, Pentium 4, Pentium D, Pentium Extreme Edition, Pentium M, and Xeon(server proc)
Intel's Processors are more of a Business and multitasking then gaming. Their Dual-core processors are highly recommended if you are going with intel(best budget Dual cores).
AMD's procs are divided into a smaller category: Sempron and Sempron 64, Operton, Athlon 64, Athlon 64 X2, and Athlon 64 FX.
AMD's processors is the best Processor if you are going gaming with a medium budget. I highly recommend their single core Athlon 64 Processors or their dual core Athlon 64 X2 procs for gaming. For budget wise go for an operton or a sempron 64.
DIFFERENT SOCKETS ARE IMPORTANT TO WHAT PROCESSOR YOU BUY! IF YOU BUY A SOCKET 775 PROCESSOR AND A SOCKET 487 MOTHERBOARD UR SCREWWWED MAEN!!!!!
For the Intel Processors They currently have 2 different types of MotherBoards: Socket 775 and 478.
AMD has 3 different types of MotherBoards: Socket 939, 940, and 754.
Onboard Video for me is only recommended if you are on a reaaly loowwww budget so I suggest you only buy Motherboards with onboard video if you are in that condition.
Onboard Sound is always included stay with it if you get a 2.1 speakers (2 speakers 1 subwoofer). If you want a 5.1 or a 7.1 then I suggest you buy a sound card.
SLI(Scalible Link Interface) is only recomended if you are gaming and your resolution is set to 1600x1200 or you will bearly see a difference normally.
CrossFire isnt recommended because its performance isnt that great and is a pain to set up.
RAM is also important .
AMD currently uses DDR 400 (PC3200) types of ram while Intel uses both DDR 400 and DDR2 667(PC5300) depending on the motherboard you buy. I recommend you buy at lowest 1GB of RAM if you want good performance.
There are currently 2 major companies that make them ATI and NVIDIA.(bit biased about this)
I prefer ATI's graphic cards for a single video card option because its performance in single out matches NVIDIA's single option.
If you are going with a dual card option go with NVIDIA's SLI rather than ATI's Crossfire because ATI's dual card solution is a waste of time and money.
I would not also go with AGP because sadly AGP is dying and also there will be no more new AGP cards later on.
HardDrives are really inexpensive because you can get a 160GB one for under 100$ .
When getting a HardDrive I recommend getting a SATA rather than any other type(smaller cords= less mess). SATAII is not recommended because there isnt much of a performance boost that you can see.
At the least do not buy a power supply Lower than 300watts unless needed too.
Ill finish later .
You also can tell me your budget for building a comp and ill give you a list of things you could buy within that budget.