AGP Voltage, A7N8X, and 9700 PRO

[scamp0000]

The reason for this post is two-fold. One, I have had problems playing Nascar 2003, getting random reboots and in-game hangs. I hoped maybe i could get some advice from others who have solved their particular problems. Two, if we shouldn't increase the AGP voltage, why do we have options? Why 1.5 vs. 1.6 or 1.7? Is this really gonna cause me problems?
To fill in some background, I have an A7N8X Dlx with an AMD 2600/333, OCZ PC2700 (no overclocks on anything). Graphics card is an ATI 9700 PROwith Cat 3.1 drivers. Running XP Pro with all updates including SP1. Also most recent drivers from ASUS website. Everything else is as new, drivers wise, as is currently available. N2003 will lock up at freakishly random intervals. I may play for 2 hours and no lock-ups, but as soon as I get in an online race, it is sure to lock-up. It may happen 30 mins in, 2 hours in, or even 3 hours in. I thought heat might be the problem, and made some major changes to my cooling including better airflow, an SLK-800 heatsink with 80mm Thermaltake SmartFan2 along with a SmartFan blowing out the back of the case near the CPU. I also bought a new Antec True 430W power supply as my old generic PS (400W) was suspect. After all this, my CPU temps dropped from a whopping 65-68C to 45-50 under load. Still had the lockups.
Since my last lockup (this past Sunday during an online league race) I have downloaded an flashed the 1002a BIOS and put the CPU fan on the "Power" fan receptacle. Works well and case is much quieter. Now for the interesting part. I bought a thermal display unit for the drive bay and attached the leads to the heatsink, hard drive and put the system lead on the 9700 PRO heatsink. I was getting high temps from the video card (at least I thought they were high). 42-45C at load in games. For the heck of it, I changed my AGP voltage to 1.7 and temps from the video card are now 37-40 at load in games. I do have the auxillary power supply hooked up to the end of the card. Talk about suprized! I actually thought they might go up. I wonder if increasing the voltage allowed the fan to run at full speed thereby cooling the card better? I don't have an explanation and hoped I could get some ideas. I haven't had another lock-up since these changes. Keeping my fingers crossed.
Thanks for any ideas.