A good middle-of-the-road rig
It sounds like the OP wants a fairly upper-midrange rig, rather than the biggest, most fire-breathing, tweaked-out whatever. Coming up with a hardware configuration in such a sea of viable choices is difficult these days, and I'm a bit worried that this will put off some less passionate enthusiasts. I want to make a good contribution to the general helpfulness of this forum, so here are my recommendations for a modest-to-high-end system for under $1200 depending on which of the hardware options you select.
Processor: Personally, I'd go with an AMD Athlon X2. I think it's safe to say that the quad-core AMD processors won't be using the AM2 socket, but the Athlon X2 processors still provide a good value while being right at Intel's heels in terms of performance. I've been an AMD guy in the past, though my latest machine (a laptop) is a Core Duo. Even though quad cores are on AMD's horizon, a dual-core processor clocked high enough should still be acceptably future-proof. It may be a good idea to not skimp on the model you choose, however. The X2 4600+ would be a good middle-of-the-road solution that should still run games acceptably well for years. If you're like me, you don't like to upgrade all the time, and don't feel you have to have the latest and most expensive of everything, just what you need to do the job well..
Motherboard: The X2 4600+ is a Socket AM2 processor, so naturally you will need an AM2 board. ABIT and ASUS motherboards have never given me significant trouble. I have an ABIT BM-6 from 2000 that is still going nicely six years later, and an ASUS A7V-266E that still works well. Granted, those are both old boards, but I've always known both companies to be reasonably conscientious. Nvidia is currently the leader in chipsets for single-card and SLI rigs, though an ATi chipset is required for a dual-ATi rig. The question to be considered here is how many video cards you want to use. My recommendation is to go with a single video card, and pick a decent one, instead of running two cheap ones, as a single powerful card will net you a greater performance gain over two underperformers in SLI or Crossfire. With that consideration in mind, there's really no reason not to pick a board with an Nvidia NForce chipset. From ABIT, the best choice in AM2 and NForce is the KN9 Ultra board, with the NF570 chipset, all for under $100. This is likely the board I'd use. The board also uses heatpipe cooling, which eliminates the need for separate fans on the chipsets. These tend to be inexpensive sleeve-bearing fans, which gunk up and fail before long anyway. The ASUS option is their M2N-E, which is slightly less expensive than the KN9 Ultra from ABIT. I don't think you could go far wrong with either board, really.
Video Card: TechGage has evaluated several video cards in the midrange category, which seems to me like a good idea since these are the cards that the majority of enthusiasts end up purchasing. The complication here is Vista and DirectX10. Microsoft has admitted to a 15% performance hit when playing DX10 games in DX9 mode on a DX9 card in Vista (which is totally
b'getto in my opinion, but not likely to change, so you still need to plan around it.) The best strategy here is to get a mid-range card now, and then save up for a DX10 card when they become affordable and widely available. This is where the TechGage reviews come in. I personally like that ASUS EAX1650XT card which TechGage reviewed
recently. This card should give you enough performance for the current games, and to tide you over until DX10 cards are more plentiful.
Memory: 2GB DDR2 800. Get your memory now, because I don't see these standards changing for a little while. The more you spend on memory, generally, the more reliable it will be. I personally feel more secure with Kingston, Corsair, Crucial, or other well-established brands, even though their product is going to cost a little more.
PSU: If the case you choose doesn't come with a PSU, you'll need one. If the case you choose does come with a PSU, it's likely crap and you'll want a more reliable, stable one anyway. The Corsair HX power supplies are made by Seasonic, and have a good reputation for being stable and reliable. Seasonic's own S12 series is also a good series. This rig should provide great performance without being power hungry, so enormous power supplies will not be required here. You want a power supply that will provide enough power for your future upgrades, which may include another hard drive or two, so look for PSUs around the 400-500W sweet spot (+/-10%). Select from these three brands based on price. Fortron-source is another good brand. Antec's line of power supplies should also get the job done well enough while being reasonably trustworthy, though I had a bad experience with the NeoHE line when it first came out. It seems that the problems with that line are mostly cleared up, though. Just pick the model that appeals most to you -- there are many PSUs that will work in this situation. The Antec NeoHE with its straight-through airflow deserves some consideration if you go with the Antec P180 case.
Case: My personal favorite is the Antec Solo, though the P180 is also a nice one if you want a bigger. These aren't the cases for you if you feel the need for bling. In my opinion, the Antec designs are very elegant, not gaudy or garish or intimidating. Pick just about whatever case you want here, and just be sure that it has enough room for the power supply you're using (as some newer high-watt PSUs will use an extended chassis). Be mindful of airflow. Setting up an effective airflow path in your case takes more than just a bunch of fans installed willy-nilly in a variety of intake and exhaust orientations. Air should enter the case near the front bottom edge, and exhaust through the upper rear of the case. The P180 is a special case with its individual airflow path for the hard drives and power supply. Antec generally knows what they're doing with case design, whereas brands like Thermaltake are more concerned with a case's "bling" factor. Tt also has a case that looks like my Harman/Kardon receiver, though the big knob on my receiver actually does something while the big knob on the Tt Kandalf, to my knowledge, does nothing.
Hard Drive: Generally, Seagate has a great quality and longevity track record. Select the capacity you want, but be mindful to select the Serial-ATA 2 3.0GB/s, 7200RPM version of whatever capacity you choose. Serial ATA 2 is much faster than the old Parallel ATA (those nasty ribbon cables). I prefer to have one big hard drive instead of multiple smaller ones. I tried that in my last machine build, and I always found I used one hard drive more than the other, which just sat there spinning but doing nothing.
Floppy drive: Don't need it anymore. You can swap one in whenever you need it without disturbing the 3.5" bay covers on your case.
Optical drive: One drive does pretty much everything these days, but if you ever want to dub from one DVD to another, you'll want one DVD-ROM to go with your DVD burner. I wonder how far out Blu-Ray writers are.
Sound card: I'm a bit of an audiophile, and I definitely notice a difference in the richness and detail of the sound provided by a good sound card over that of your typical onboard sound. The onboard sound usually has a higher noise floor as well. You probably won't notice too much of a difference between the new Creative X-Fi cards and the older Audigy cards, especially if your music is compressed in WMA, or if you're not purchasing a high-end audio set like the Altec Lansing FX6021/PT6021, Klipsch ProMedia, Logitech Z-series, or Cambridge Soundworks Gigaworks. If you have any of those, and are a real stickler for sound quality, you may want to spring for the X-Fi.
Hopefully I've covered most everything you'll need to think about. It looks like you were wanting someone to help make your decisions, so this should be a good rig for you that will still be an acceptable performer in two or three years, with future upgradability. If AMD's quad-cores come out, or if you decide to go Intel, you'll need a new motherboard, but the old RAM should still be usable. The other concern is Vista -- if its computing requirements are just totally through-the-roof, you might be upgrading in a year and a half instead of two or three years.
It bears noting that I'm not the most expert of experts on this subject, and there's the possibility that I might have missed some fatal detail. I hope the other members of this site will review this list I've proposed and comment. This should be a good rig at under $1200 with case and power supply.
All the best,
Tw
Maybe you guys could tell me what parts I sohuld get. I play games like Counter Strike Source and Battlefield 2 and I have about $1200 to spend 
