I Have an Intel Dualcore 2.50GHz with DDR2 Foxconn G31 motherboard with 450w power supply but the only thing i worry is my PCI-E v1.0 . Will it support for GTX750 ?
On such an old system and with a somewhat low-end video card, I really don't think you're likely to notice performance limited by PCI-E bandwidth. Much more likely that your aging platform will drag down performance, if anything.