Most 810s dont have an AGP slot... so even if u have one it will prolly be AGP 2x which is no longer supported... Seriously, very seriously, you need to upgrade within a month... U can opt for old PCI cards tho... but they are worthless buying IMO...
Ps. Remember to quote yr budget while asking for some buying recommendations
810 has only a PCI slot. try getting a XFX GeForce 5200 card, which is available in 2 versions-:
128 MB= Rs 2500
256 MB= Rs 5000-6000
I would recommend the former coz both have the same GPU, and increased mem isnt going to make much difference.
BTW, upgrade ur RAM to the max possible to improve the performance of the PC as a whole.