I'm a computer guy, so please don't get too mad for this question (I read over the "Is this too hot?" sticky already...) I've never had this problem, or just about any problem, with my computers before, however, and I really don't know what to do.
First off, here is my setup:
Asus A7N8X Deluxe
AthlonXP 3200+ (at stock speed)
Volcano 7 (I don't believe it's a 7+...)
nVidia GF FX 5950 Ultra
Corsair 1GB (2x512)
PSU is whatever came in this iCute case. It claims 400W max power.
Fans are: 1 side blowing out; 1 top blowing out; 2 back blowing out; 4 front blowing out; PSU has a fan blowing out. Nothing is taking in cuz it sits under a desk and it just doesn't seem like any decent air will be had around there...

I think that's the main stuff necessary here. Check my profile for more info.

Basically what's happening is whenever I load up Counter-Strike: Source, I can play for about 5-10 minutes before the computer just locks up entirely (any sound that was playing will just loop in the speakers until I hard reboot). I check temps in the BIOS after such an incident and it claims to be at around 49-50°C. Now Asus PC Probe, assuming it's somewhat accurate, rates the temps at 41-43°C while idle, then it jumps to 45 or more when playing original Counter-Strike or something.

Temperature in the case sits around 26-28°C.

Now before I continue, until two days ago I was running an XP 2500+ on this same setup, and temperatures idled around 37-39, then jump to 40-42 under some load. Counter-Strike: Source crashed just the same, however.

Last week this symptom started occurring any time I would load even regular Counter-Strike, and also while logging in to Final Fantasy XI. I couldn't even play the games for a few days. I took the computer out to my dad's shop and used the air hose on it to blow out all the dust (there was a ton of it), and that seemed to fix the lockups in CS and FFXI, though Source still suffered.

Now that I'm on the 3200+ I was kinda hoping this would just go away, I thought maybe my CPU was getting burnt out. This CPU idles hotter than the last, but the exact same problem is occuring. I actually just had it happen while playing FFXI for about 3 minutes randomly...

Could this be the temperatures of the CPU in any way? Could that Volcano 7 just not be cutting it? If so, what are some excellent (price doesn't matter) fan/heatsinks for this CPU? It could be that this fan just isn't cutting it under a real load (and CS is pretty old, it doesn't tax things too much...)

Like I said, the XP 2500+ ran cooler but suffered the same symptoms, but could that just be different acceptable temperatures for these CPUs?

Could it be the video card at all? What happens when video cards are getting too hot? Right now at idle the GPU core is sitting at 43°C and the ambient is at 38°C.

I wasn't sure if too much crap was hooked up to the PSU, so I unhooked a DVD drive that I never use as well as three outgoing fans, but no to avail.

Sorry if these are questions you guys get all the time, I just really don't know where to take it from here. I've honestly never had trouble with any computers I've had, so I'm kind of at a loss as to a cause I'm thinking it's heat, but I really don't know for sure.

Any help would be greatly appreciated.

Your side and front fans should be pulling in air and the rear fans discharging it.
There are programs that will tell you your system temps like Motherboard Monitor. The stock fan that came with my processor failed after a few weeks. I replaced it with a Speeze. Those nVidia cards get really hot so that ads to the inside temps. Have you tried gaming with the side panel off the case. If you dont have the problem with the case open then its deffinately heat.

I got the information wrong in the original post now that you mention it. The four fans in the front of the case are indeed pulling air in. The side, top, and back fans are blowing air out, however. The side sits off the case anyway and is next to a wall kinda, so the fan on it really doesn't do much anyhow. I always leave the side off the case but don't see any difference.

Changing your HAL is never a good thing. Although it is not as bad switching from ACPI to APM as it is from APM to ACPI, it is still not a good idea. If you disable ACPI in the bios, Windows will still be using an ACPI HAL, and will expect ACPI-compliant hardware.

If you change the HAL in Windows, you still are running risks due to resource assignments being a part of the hardware profile, not just dictated by the current HAL.

I went through something similar with 2 nForce boards. The system would run fine until I tried to game or do anything with multimedia. It turned out the RAM timings were set too aggressive. I didnt notice at first that the timings reset when I changed the main setting to Expert so I could bump up the bus speed.

I don't believe it's sound card related, I think the sound repeating is just a symptom of the system locking up until a hard reboot.

I bought a new Zalman fan last night and managed to play Source for a good hour with no crash, but just my luck the PSU up and died on me. I went and bought a new Enermax 470W today and started booting, but something happened with the boot hard drive, so I guess I've got some troubleshooting to do. Basically it's no longer bootable, and in the BIOS it's showing up as running in PIO mode instead of ATA100

My memory timings are all at the default setting of "optimal," not sure that that would be an issue (I don't think...)

Well, I don't know. My whole computer is messed up, so I guess I gotta buy a bunch of new **** to try and figure out what exactly is bad. I can't tell now if the main hard drive has failed or if the motherboard is going bad. The OS boot drive is detected as 8455MB instead of the 120GB it is, and the BIOS loads pitifully slow throughout the entire process. I'm wondering if the motherboard is just shot somehow...

Before you spend any money, try taking the CMOS battery out for a few minutes, then reinsert it and set your BIOS to the default or optimum settings.
Try booting.

I had this problem not too long ago, I just fixed it. Apparently the updates for my mb, not the BIOS ones, just the other stuff. It seemed that when I didn't install the new drivers from the manufacturer the game ran fine. I haven't installed the drivers again to see if it was truly the problem, but it seems to have been. I put the timings in a fail-safe type of setting, and it still locked up. Try installing Windows again, and not updating, or if you have roll back or etc. try that.