Ok.... rather than set up a tutorial thread, let's make this into a Q & A sort of thread and the emphasis will be on setting up your PC regardless of the specs. Remember, however, that some pc configurations are not compatible with audio no matter what you do. Also remember that most pc's coming out today have a decided slant towards powerful video capabilities, something which often conflicts with glitch-free audio performance. If you are decided about great audio performance, you will have to give up great video performance (which means you will have to give up that 8800GTXProMillenium+1 and go for a considerably less powerful vidcard).
I know this thread will get unusually long so I will be adding to it as time progresses. Any pertinent info will be added to this initial post and I suggest that anyone posting new questions refer to this first post so we can avoid duplication.
One of the most important considerations when choosing a pc for recording happens to be not the pc, but the SOFTWARE.
Strange, but true. It is the software that determines what soundcard you will use, and what the minimum requirements are for running that software. Word of advice about minimum requirements... follow that and your pc/software combi will function, but just barely. You need to factor something like 150% of the minimum just to have something workable; so if the minimum cpu is 1 GHz, you really need at least 1.5 GHz to be able to do any real work... 200% to 300% of minimum is suggested.
Software also determines the platform you will use. Sonar, Audition, Wavelab and Soundforge are strictly pc while Logic, Digital Performer, Bias Peak and Soundhack are mac. ProTools, Cubase and Nuendo are dual-platform applications. Let's not turn this thread into a mac vs. pc thread because, in my view, these are nothing but tools... machines that are designed for a purpose. Each has it's strengths and weaknesses and I'd rather we concentrate on how we can maximize the usefulness of these tools. No mac vs. pc flame wars, get it?
Now that you've decided your software, if you do some digging into its feature, you will often find a list of compatible soundcards that go with it. Please, please choose a soundcard with a known compatibility. If you decide to use that cheap 300 peso CMI soundcard or USB cdrking sound dongle, your on your own. I have nothing against using inexpensive gear but often you will find that support is sometimes non-existent or that drivers are POS and are hardly updated. To add insult to injury, the performance of these cheap cards are often not up to par and sound quality often suffers. You CAN use these cards (I did not say you can't), but you will have to work extra hard to get even demo quality sound from them so if you decide to go that route, don't forget that I told you so. I have used soundblaster cards early in my delvings into digital audio and over the years, my ears have become attuned to what they can do well, and what they cannot. I will say that blasters are good for learning the craft.
Now, finally, the pc...
So you got your software and you've chosen your soundcard... now what? Put it all in that pre-assembled pc and then click on that record button in your software and hope you nail that perfect take? NOT!
Most pre-assembled pcs skimp on some important very important parts like the motherboard, ram, vidcard, power supply... you name it. Even Dells are guilty of this fact plus, pre-assembleds are more tuned towards office applications and the occasional game or 2. Audio pcs are a different breed. Audio pcs eschew 3D video performance in favor of increased audio capability. Capabilities like low latency, high track counts, quiet operation and very good 2D screen redraw performance (playback of movie videos is also a consideration for post production suites).
Some soundcards are also picky about the motherboard chipset. Research well on the chipsets that go with your soundcard. You don't want a repeat of that Via debacle that happened with soundblasters. Via chipsets starting with the KT166 were horrible with computer audio; it was only with the K8T800 Pro chipset that Via redeemed itself. Intel chipsets were stable with the i865 chipset, but the i915 and i925 were disappointing for some; the present 975XBX and 965P chipsets are proving to be very good performers. Nforce chipsets were quite good up to Nforce3, the Nforce4 was a disappointment plus the combination of pcie proved to be a real problem. If you already have chosen your software, it pays to lurk in their user forums since they often post which motherboards work well - that's how I happened to choose my present day N3 mobo.
So what does this mean for most pc-based platforms? DIY systems are the way to go. You get to choose your own parts and you can most likely get the best and most compatible components for your needs. At times you can save a lot by going DIY but you then have the responsibility of installing the OS, tweaking it for audio and installing all the software and hardware; a process that can take 2 or 3 days at least. Mac users have it easy, their machines just work out of the box but they have to pay for that ease of use (I call it the 2:1 ratio but lets not go into that).
There are lots more to discuss but let's take it one step at a time.