Workstation Hardware Support

I have two custom built work-stations and their build is:
-COOLER MASTER COSMOS ESA RC-1010 Steel Full Chassis Silver Full Tower Case Retail
-ENERMAX EGX1000EWL Galaxy DXX 1000W Power Supply
-Tyan Tempest i5400XT- S5396WA2NRF Workstation Board. Size Extended ATX 12” x 13”
-2 Intel BX80574E5420A CPU Quad-Core Xeon E5420 LGA771 2.50GHz 1333MHz 12MB 80W Active Retail
-16GB (8x2GB FULLY BUFFERED PC5300 DDR2 667 ECC (FB-DIMM)
-4x SEAGATE Cheetah 15K.5 ST3146855LW 146GB SAS 15,000 RPM 16MB
-BFG Tech BFGR88768GTXOC2E GeForce 8800GTX 768MB 384-bit GDDR3 PCI Express x16 HDCP Ready SLI Supported Video Card (supports Max. resolution of 2560x1600)
-XP Professional - X 64 Editions

I still have one tower running the Tyan motherboard that gave out in the other. I have a ton of problems and with the configuration I have, I don't have access to all the power of my hardware. I run a CS3 package (Adobe Premiere Pro, Photoshop, etc.) And these programs are very RAM intensive. Any my workstation regularly crashes. It shuts down on it's own. It runs slow. I can't connect to the internet, and the USB ports in the front don't work. I assembled this computer myself and I happen to suck in doing so. But I had to make do with what I had. While I've ordered a new motherboard for tower that won't work, I need to fix up this faulty but working tower. I could really appreciate any input that you guys provide.