LGA775 is the latest socket type for Intel chips. It's also called Socket T (I think it was codenamed Tejas, but anyway..) Thats the one I'm using (building right now actually)
LGA stands for Land Grid Array, and the 775 is how many contacts (previously called pins) it has. Before LGA, we had PGA which is Pin Grid Array. I don't like these if you bend a pin, you are screwed. Doesn't usually happen, but my dad has done it, broke one clean off. I bent one, but we fixed it.
Socket 478 is one step behind LGA. It is a PGA style chip with, you guessed it, 478 pins. We are using these for the school district installs, and they are a fine intel product.
The thing to remember about LGA775, is that the board must support it, and the board you choose will likely have PCI express instead of AGP and minimal PATA support. This isn't necessarily a bad thing, they are forcing use to use the new standards, but some people are put off by that. Just something to keep in mind.
as for boards, mATX i think stands for mini ATX. I like to go with just standard ATX, because I'm not building a small form-factor pc.
the first board you listed, i found for cheaper, with free 2day shipping, from a reliable source:
http://www.zipzoomfly.com/jsp/Produc...uctCode=240936
all new memory are DIMMs. All you need to worry about is whether it is DDR I or DDR II. There is also some more confusion to add to it, when you are talking about the speed of the memory. PC3200 = DDR400. Why they do this, I still don't know, but the 400 means the memory runs at 400 Mhz. This is the fastest DDR I memory that you can get, at least as far as I know.
As for the board, Intel makes fine boards, and you are assured of compatibility. My dad swears by them, but I wanted something a little more flashy, thats why I went with a Gigabyte Duo board.
Go down this list:
http://www.zipzoomfly.com/jsp/Produc...& Brand=INTEL
and you'll see the price difference and what features are available. 925 is the latest chipset version, but 915 is still very new also.
Honestly, I'll get back to you on which board is the best bang for the buck.
Hard drives, again look here:
http://www.zipzoomfly.com/jsp/Produc...oryCode=011016
I would stay with Western Digital and Seagate, although I know many people would disagree with me. Hitachi and Maxtor are okay too, but they aren't my first choice.
both the drives you chose will work fine with your board. that board has 4 SATA channels, and one PATA channel (You can run two devices on one PATA channel, using master and slave settings)
Most DVDRW drives come as combo drives these days. this means it will write DVD +/-R/RW and CD-R/RW and probably some more formats you won't care about. I currently use a TDK 880N which is a fine drive, that burns DVDs at 8x and CDs at i think 32x.
I just bought a Dual Layer Sony drive DRU710a, that still supports DVDs and CDs, but will burn Both layers of compatible discs. This means that if I have a movie from the store that I want to make a backup of, and it is in the DVD9 format, which is about 8.5 Gb, I can make a 1:1 copy of it; no compression! (currently, my drive only supports DVD5, which is the standard 4.7gb discs. Having a movie I want to copy that is almost double this size is a problem, which is where programs like DVD shrink come in handy.)
As far as making videos you can watch on your settop box, thats a whole 'nother can o worms. In short, you will be able to make those kinds of discs using your DVDRW drive, about 10gigs of free hard drive space, DVD Decrypter (free program), Nero (not free, but crackable), and blank DVD+R discs (not free, but cheap these days $20 for a 50 spindle)
and yes, DVDRW functions as DVDRom.
video cards, ah this is fun. a lot of them have S-Video outs, so you don't have to worry. I think they also call this DVI out, but I'm not sure.
Anyone else, feel free to chime in here. If you want to play Doom3, you're in luck. Doom3 runs extremely well on lower end cards. check out this:
http://anandtech.com/video/showdoc.aspx?i=2146
that will pretty much tell you whats what. I went with an XFX Nvidia 6600 GT 128mb. Although, from what I've read, having 256mb of video memory will make a significant difference in Doom3. Things to check out when considering a video card is FULL DirectX 9 support, and the latest pixel shading.