Help: Music PC Crashes

Hello Major Geek Gurus,

Please excuse the fact that I'm a newb!

I am looking for help with my custom pc. Ever since I got this thing it has crashed on me. Sometimes it just shuts off like its overheating even after adding an extra fan...and other times I get the BSOD.

I have replaced the PSU twice, replaced the mobo, updated the BIOS, Drivers on all peripherals, Windows updates, checked the RAM, and still...crash, crash, crash.
This is a music pc, so I have software like Protools LE 7.3.1, Sibelius 4, FantomX Editor, Creative MediaSource 5, iTunes, Cubasis 4, Fruityloops, and about 3 other programs for music. But these problems happened before I installed any software.

I usually keep cool, but I am losing my mind. I am almost positive it's either drivers or hardware (either soundcard or videocard) Anyway, here's the specs:


- OS - Windows XP, SP 2
- AMD Athlon 64 3800+ Processor
- 2 GB DDR400 Dual Channel Performance Memory
- nVidia 6600LE 128Mb DDR Video Card
- Hard Drive 1 – WD 40GB 7200 RPM SATA3
- Hard Drive 2 – WD 160GB 7200RPM SATA3
- Creative Sound Blaster Audigy2 ZS Platinum 7.1 Channel 24Bit 192KHz Sound Card
- Lite-On 16X DVD+R; 8X DVD+RW; 8X DVD+R DL; 16X DVD-R; 6X DVD-RW; 5X DVD-RAM; 16X DVD-ROM; 48X CD-R; 24X CD-RW; 48X CD-ROM
- Windows XP Home

Detailed Specifications –
Processor:
- 2.4Ghz Clock Speed; 2Ghz Front Side Bus; 128KB L1 Cache; 512KB L2 Cache

Memory:
- 2GB (2 x 1GB); 184-Pin DDR SDRAM; Cas Latency 3; Timing 3-4-4-8; DDR400

Video Card:
- Core Clock 310Mhz; 4 Pixel Pipelines; Memory Clock 400Mhz; 128MB; 128-Bit; DDR; DirectX 9; Visa Ready; Max Res 2048x1536

Sound Card:
- Audigy2 Chipset; 7.1 Channels; 192KHz; 24-Bit; 108dB SNR; Dolby Digital EX 6.1 Hardware Decode; Polyphony 64 Voices (Hardware)

Power
- 450w Power supply (not a cheap one)
- Cyberpower UPS

Ports:
Data:
- 8 x USB 2.0 (2 on Front)
- 2 x PS/2
- 2 x IEEE 1394

I also use external hardware like the MBox 2 and FantomX8 Synthesizer, if that helps, but it still crashes even when neither are plugged in.
I looked at so many sites for tech support and I think this website is the most knowledgable. Any helped would be greatly appreciated.

Thanks!