I gave up on Q6600 and RMA'd back. Put back in E6600 and in the meantime found that power supply to MB was only connected with 20 pins. I corrected to 24 pin connection and board seems much more stable.

I have OC to 2925 Mhz on the chip leaving DDR-2 at 800.

System appears pretty stable and have run:

Prime95 2 hrs
Everest Stability 1 hr.
3DMark Advantage both in Performance and in High
PassMark Performance Test 6.1 (2 runs).

During all of this I recorded the following in Everest Monitor:

Temps:
MB 39C min 41C Max
CPU 34C min 43C Max
Core1 30C min 50C Max
Core2 28C min 50C Max
GPU 56C min 81C Max

CPU Fan 2836 min 2909 Max
GPU Fan 1196 min 1515 Max

Voltage:
CPU Core 1.26 min 1.34 Max
+3.3V 3.33 min 3.34 Max
+5V 4.95 min/Max
+12V 11.97 min 12.03 Max

SYSTEM DESCRIPTION:
Windows 32bit Home Premium; ASUS P5N-E SLI; E6600 with Artic Freezer Pro 7; Corsair DDR-2 XMS 2x1GB; Corsair 750W PSU; Raid 0; SATA HDD's; Apevia X-Cruiser Case; 120mm exhaust rear; 80mm exhaust top; 2x80mm intake front; 80mm intake side; Antec GPU slot cooler. BFG 8800GT OC 512MB.

My main query involves the settings I have used in Bios at this OC. I do not know the function of some and am looking for sage guidance from the more experienced of you on this board to see if I should make any further changes.

AI Tuning = Manual
NB PCIE Frequency = 100
VCore Voltage 1.32500 (same as shown in Core Temp program)
Memory Voltage = Auto
NB Voltage = Auto
VCore Offset = Auto

Mem Clock Mode = Unlinked
FSB = 1300
Memory = 800

CPU Internal Thermal Control = Enabled
Limit CPUID Max Value = Disabled
C1 (C1E) = Disabled
Execute Disable Bit = Enabled
Virtualization Tech = Enabled
SpeedStep = Disabled
Multiplier = 9X

Memory Timing:
tCL = 5
tRCD = 5
tRP = 5
tRAS = 18
CMD = 2 clock
tRRD = Auto
tRC = 22
tWR; tWTR; tREF; tRD; tRFC and Asynch latency all set to Auto

LDT Freq = 5X
SLI Broadcast Aperture = disabled
Spread Spectrum (CPU; PCIE; SATA; LDT) = Disabled

DRAM:FSB Ratio shown in Everest = 16:13

I would appreciate any comments and education that you can supply. I wish to leave the OC on 24/7 and want to ensure I am in a "safe" setup. If this performance cannot be maintained I am looking at the E8400 for this system but hope to wait out for another year or so. I moderately game; do quite a bit of audio/video; and work with very large spreadsheets with complex macros.

Thanks.

You'll be fine with those settings, well within 24/7 operating limits. Only thing I'd advise is run Prime95 small FTT and blend for longer than 2 hour each. For me I do small FTT 6-8hours and blend 10-12 hours.

You can probably tighten the ram timings, to 4 4 4 12.

Thanks for the information. I will try to tighten ram as suggested. Good to know this is a safe setup to leave in place.