Okay, the onboard chipset/video is probably sis, so that's why that driver is showing up. You have to disable the onboard video through the BIOS before installing your new card.
 
If you haven't done this, we'll give you instructions on how to do so. If you have already done this, you have to remove/uninstall the old drivers(sis) before installing the new nVidia drivers. To do this, right-click your desktop, select Properties/Settings/Advanced/Adapter/Properties/Driver/Uninstall.
 
I don't seem to have any luck with new drivers from nVidia, so I stick with the 77.77 drivers, work like a charm for me, I used them with my old ti4200, and I now use them with my 6600GT AGP, give them a shot: http://www.nvidia.com/object/winxp_2k_77.77.html
 
Be sure to uninstall the old drivers first, then run Driver Cleaner Pro: http://www.drivercleaner.net/ before installing the new drivers.
 
The newest drivers from nVidia are optimized for the newest cards, mainly the 6800/7800 series of cards. The 81.95's kill my card, slow everything right down, so as I said, I stick with older drivers. Let us know how it works out for you.

thats the problem...my onboard is intel chipset not SiS.i uninstalled the drivers.but in bios there is no option for disabling the onboard chipset.i hav also updated the chipset drivers.as far as the newer nvidia drivers go(even 71.84 for that matter),when i try to run them it says "the nvidia setup prog could not locate any drivers for the device"
also the sisgrp.sys and sisgrv.dll are provided in the installation cd of the geforce card and the comp copies these files from th card.
so does this mean i hav a SiS card and not Geforce.
and how do i update the drivers in that case

Perhaps, if you could relate the motherboard manufacturer and its identifying number, it would be helpful. Generally, onboard video can be disabled through the Bios. In your case, if this is not so, there may be a toggle on the motherboard that needs to be reset.

my motherboard is asrock P4i45GV.it has intel chipset 845.
thats what beats me.how does the dxdiag show main driver as sisgrv.dll
i also looked up in driver details of the card in device manager and found that most of the files were starting from the letters "sis".i also found these files in the installation cd given with the card.
and as i said dxdiag shows agp accleration as not available.maybe i hav to update the drivers but what drivers do i install as the nvidia drivers from the site are not working.

Apparently, Asrock did some interesting engineering on the chipset in your card. The AGP slot is not really AGP but something called AGR sometimes and AGI sometimes. I found the manual for your motherboard here: http://www.asrock.com.tw/Drivers/Manual/775i45GV.pdf
The thing is that not every card is compatible with this kind of setup through an AGR/AGI slot. You can go to the Asrock Download website here: http://www.asrock.com.tw/support/Download/index_download.htm . In any case, the problem you are having is with the way that the "AGP" slot is engineered for your machine.

so it seems there is nothing i can do..anyways thanks a lot for all the trouble u took..
seems i will have to do away with the card....

You might look through the manual. On pages 7 and 8 they do list what cards are compatible with their setup. You may be able to use that same card but produced by a different company.

thanks a lot.will try something else as u say

That just plain blows. ;(
 
I hope you can return your vidcard, or at least exchange it for one that is compatible with your mobo. Good luck dude.