not really, the PC will not use 750W, it's what the PSU is capable of power; your bill will depend on the components you use

now i get it thanx.
that the reason why i afraid buying a PSU with higher watt.:^D

uhm... I don't think you get it quite

if you run your current system with 400W PSU or 750W PSU with same efficiency rating, you won't be using more power.

i think higher watt PSU mean higher bills but i wrong.

I think the efficency might be lower ebcause you don't run it in the optimum range.

well, it's far from bad at "middle" usage (~400W)

http://www.jonnyguru.com/PSU/ST75ZF/index2.htm

does computer need AVR(Automatic Voltage Regulator)?

why my +12Volt Not show 12.00volt? currently it shows 11.673.

My +12volt rail show 17A but my geforce 6200 need 18A i think this is the problem because when i play F.E.A.R it suddenly crash.

There is no way your 6200 card needs 18Amp*12 Volt = 216 Watts of power; I don't care what game you play/