Well i have 2 power supplys 1 is 400Wats and the other is 200watts can i run my motherboard on 200watts and graphics card on 400wats. Is it enough or i should buy 600watts power supply but i am a bit low on budget is 200+400 watts power supply works then i will go with 400+200 wats power supply and will buy 600watts power supply later.
It'll surely work.. However the procedure is a bit tricky and not as straight forward as using a single PSU.. If you have no prior experience or have no direct technical assistance available, spending a little and getting a single good quality 550W PSU is what i would recommend.. What are your other system components btw.? Specify the make and model of both the PSU's also..
A 450W PSU is the minimum recommendation for a system containing a single GTX460.
I don't think it is worth the risk of damaging your components to mess around with two PSUs of indeterminate quality. Kludging a multi-PSU setup out of them is likely to introduce still more electrical noise. In your case, I would get a quality 500W PSU (like Antec, Seasonic, Corsair, or Enermax). The best thing to do is wait until you can afford that, or consider buying a lesser GPU in order to get the better PSU first.