these are the processors, I have to choose one of them...
-Intel Core 2 duo E8400 Wolfdale        http://www.newegg.com/Product/Prod [...] 6819115037
-Intel Xeon E3110 Wolfdale       http://www.newegg.com/Product/Prod [...] 6819117165
-Intel Xeon 3085     http://www.newegg.com/Product/Prod [...] m=N82E1681
-Intel Core 2 Duo E6850 Conroe       http://www.newegg.com/Product/Prod [...] m=N82E1681
Or maybey??
-amd athlon 64 X 2 6000 + windsor  http://www.newegg.com/Product/Prod [...] m=N82E1681
-amd athlon 64 X 2 6400 + windsor        http://www.newegg.com/Product/Prod [...] m=N82E1681
 any recommandation?? here my processors thread: http://www.tomshardware.co.uk/foru [...] ng-desktop
 
Now I need a good motherboard
-what do motherboards do exactly?
-what do I have to look for in a motherboard? (what makes a mobo good?)Now I'm looking for the right/best motherboard
 
I want a very fast mainly gaming computer... my budget is 1500-2000$  - 200$ for the processor
I'll be playing a lot of games like WOW, assassins creed, CoD 4,.....  (at high quality)
and also a lot of downloading movies etc...
If u need to know anything else say...
 
thank you very much!!!

Can't necessarily say what's the best mobo, but I've been using an ASUS X48 Rampage Formula for the past couple months with my QX9650 and I'm very happy with it and all the BIOS options it provides. This mobo presumes the use of ATI cards, so if you intend on Nvidia, look to one of the 780i or 790i boards. Not sure what would be best in that group.

My recommendation (assumes no SLI//CrossFire):

E8400

8800GTX/9800GTX if possible or can be had for smiler/close price as 8800GTX, possibly a 4000 based card depending on performance/price

ASUS or Gigabyte X38 board. (ie ASUS Asus X38 Formula, X38-DS4)
X48 is kind of an overkill providing theat Nehalm is just around the corner

Corsair 650/ PP&C 610 or better (don't skimp on the PSU!!)

2GB+ DDR2 800 (or higher if motherboard is compatible with RAM like DDR2 1066, be careful when going beyond DDR2 800, as there might be compatibility issues)

Any case,etc you need.

A Xigmatek HDT-S1283 if OCing on air or a water cooled setup.

All should add up to ~$1800-1850.

---------------
E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)  

Given that the difference in X38 vs. X48 is $40 (Maximus Formula vs. Rampage Formula @ NewEgg) I'd say go with the X48 Rampage.  X48 is not the exact same thing as X38 and $40 is what you waste on half a decent dinner...don't skimp, you're putting together a nice machine.  You can do an X48 from Gigabyte if you don't like Asus' offerings or want something slightly cheaper:   http://www.newegg.com/Product/Prod [...] 6813128336
 
Besides, Gigabyte purports that Asus uses non-Japanese (and therefore obviously inferior quality) capacitors.    
 
I love my Rampage Formula.

^Good point. With the price of $30 more and with a budget of $2k might as well get the X48.

---------------
E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)  

But there is no significant benefit of going x48. Its not a matter of "don't skimp" as much as it is "don't waste".
 
My recommendation ga-x38-ds4.

^Well there is no significant gain, but might as well spend the extra $30 to get native 1600FSB of X48, esp. with a budget of $2k.

---------------
E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)  

I'd like to see a benchmark where they pit say an X38 vs. X48 with various brands (Maximus Formula vs. Rampage Formula) and truly see that they're the same thing.  I'm sure this has been done.  Either way, unless the X38s are faster than the X48s I would (go with an X48 on a mid-to-high-end build).  The cost differential is just not that much IMO.

these are the processors I'm choosing one of them...
-Intel Core 2 duo E8400 Wolfdale        http://www.newegg.com/Product/Prod [...] 6819115037
-Intel Xeon E3110 Wolfdale       http://www.newegg.com/Product/Prod [...] 6819117165
-Intel Xeon 3085     http://www.newegg.com/Product/Prod [...] m=N82E1681
-Intel Core 2 Duo E6850 Conroe       http://www.newegg.com/Product/Prod [...] m=N82E1681
Or maybey??
-amd athlon 64 X 2 6000 + windsor  http://www.newegg.com/Product/Prod [...] m=N82E1681
-amd athlon 64 X 2 6400 + windsor        http://www.newegg.com/Product/Prod [...] m=N82E1681
 any recommandation?? here my processors thread: http://www.tomshardware.co.uk/foru [...] ng-desktop
 
Now I need a good motherboard
-what do motherboards do exactly?
-what do I have to look for in a motherboard? (what makes a mobo good?)

Q: What is a motherboard (mobo)?  What do motherboard do exactly?
A:  http://en.wikipedia.org/wiki/PC_motherboard

Q:  What do I have to look for in a motherboar?
A:  Form Factor (i.e., iTX, mATX, ATX).  Compatibility.  Expandability.  Durability (i.e., solid capacitors).  Features (i.e., over clockable?  ease of over clocking.)  Manufacturer's history and reputation.

So what Mobo has all the features I need?

^ASUS Asus X38 Formula, Gigabyte X38-DS4, DQ6

---------------
E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)  

Well, there's a lot of info in towards the top of this thread, but you'd be safe with a P35 or X38 (intel Chipsets).  I'm not going to recommend any nVidia 700 series chipsets right now due to info/rumors that there's some data corruption issues and from what I gather you're not into SLi.
 
Nice boards, lots of features, all that you need and then some:
http://www.newegg.com/Product/Prod [...] 6813131219
 
http://www.newegg.com/Product/Prod [...] 6813128089
 
Middle-of-the-road (intel P35 chipset)
http://www.newegg.com/Product/Prod [...] 6813131275
 
Popular & economical, good simple basic (if you're looking to stay on the cheap):
http://www.newegg.com/Product/Prod [...] 6813128337  

Whats SLi?
And it hasnt got to be cheap
What does the quality of the motherboard determine? the speed of the computer depends of it? or quality of the screen display?

 
Vs, you're killing me.

lol srry p
I just want a good desktop and I have no clue about what to choose...

How much are you willing to spend on the motherboard?  $100  $200  $300?

get the e8400 wolfdale or get a quad core q6600. but i belive 2 cores is plenty performance. my e4600 is amazing, no oc too. as for a mobo, if no sli, then a gigabyte mobo is good. GA-P35-DS3L is the way to go. make sure the ram u get is on the mobo's compatible ram list. Crucial Ballistix 800mhz Ram is good. I wouldnt get 1066mhz ram though. as for a powersupply, get a tried and true model, i wouldnt go with the new brands. corsair let me down, giving me 5 minutes to run before it powers down, then it wont even turn on later at all. swapped out for my antec  neo he 430w and it ran rock solid since. the psu was a new one , the corsair tx750w. anyways, get an antec, or one of those hx620w corsairs or something. i have an 8800gt and a dual core on my 430w with 3 16a rails. if ur going quad then get the 550w model