VNF4 Ultra questions

Just assembled new PCI-E system and have some issues.

VNF4 Ultra
A64 3200+ S939 Win
2x512 Corsair TwinX1024-3200C2PT
Western Digital 400JB 40GB IDE
1 optical drive (Sony DVD/CD-RW combo), no FDD, using onboard sound &
onboard ethernet (no other hardware installed)
Sapphire X800 GTO 256mb

Routine format and install of XP Home as well as all the drivers that
came with the board (3.6), including NV firewall and Realtek etc., Have
Directx 9.c and new ATI Cat 5.10's with Control Center.

Have read several reviews that mentioned using the top two DIMM slots as
opposed to the lower two (which, according to the manual means using
slots 3 and 4 vs 1 and 2) for a 2-stick RAM setup, for various reasons.
One stating better stability and voltage performance in OC'ing and
another implying Chaintech support specifically recommended to them
using the top 2 slots with a 2 stick setup vs the lower 2 slots for best
performance/stability. Any experiences/opinions on this?

My Antec TX 640B case has two front USB ports. Initially I connected the
lead for them to one of the MOBO's 3 USB connectors but the front jacks
are not working. (The 4 at the case rear work fine). I tried one of
the other connectors and it likewise does not enable those front ports.
Are these enabled in the BIOS? I insured the USB keyboard support was
enabled. Device manager confirms USB 2.0 host/root installed/working
properly. I could use a clue.

Have installed all my normal tools, utilities, programs, and run them
OK, have run defrags, net-surfed, etc., - all great. Decided to install
the benchmarking utilities and run them before installing some games and
first up Aquamark3 ran great until the final explosion scene where it
crashed and caused a reboot. Same thing happened the second run.
3dmark2003 runs 3/4 of the benchmark smooth and with great framerates
then suddenly crashes and the PC reboots. 3dmark2005 same story - almost
finished then reboots. Running MPEG video trailers in windowed mode is
OK but when going to full-screen they crash midway through. I have
disabled NV firewall without making a difference. Uninstalled the Cat
5.10 and control center, used driver cleaner then tried the 5.9 and
regular control panel - same problem occuring.

The system temp is showing 35-38, the CPU temp 31-34 range, and the
Sapphire GPU runs anywhere from 48 through 78 from what I've seen
(outside a running 3d app anyway). I have seen it reach 84 with its fan
running 96%. There are no artifacts or visible slowdown before the
shutdowns. The Aquamark shutdown does present an error message referring
to an attempted access to an unauthorized region. All of the Catalyst
options are at default.

I RMA'd the GPU assuming it is the culprit and should have a replacement
in a few days, but I guess I should have run Memtest86+ first. Any
ideas are appreciated.