Windows 7 - is it enough for 9800 gx2 ?

i have thisPSU :
problem is a) after updating nvedia driver system reboot (shutdown & start ) when try to run WEI before completing assesment. {SOLUTION} generic microsoft driver or nvedia 191.07 not older or newer,or downclock vedeo card .
b) when run DMARK VANTAGE system reboot at starting test 1
{SOLUTION} downclock vedeo card
my vedeo card e-GeForce 9800 GX2 SSC clock 675 i have to decrease to 600 and shader from 1674 to 1492 and memo from 1050 to 790
i think buying another psu but i want to be sure first , because as i said i can pass wei with default card setting if i install 191.07 driver i mean if it is a power problem why it passes with that driver.
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GX2's arent traditionally the best performing cards. 2 9800's or 8800's would perform better. that does seem about right. maybe update drivers and try again.

sorry , i am asking here about my psu not performance .....is the problem (system reboot ) because of psu?

whats your psu make/model/wattage?

Newegg.com - A-Top ATP-AP700SC 700W ATX12V2.2/EPS12V SLI Ready CrossFire Ready Power Supply - Power Supplies

make sure your spreading power evenly between the rails. that psu should be enough.

HOW ?

honestly no clue. never used a duel rail power supply before.