Inno3d 450GTS No Display During Boot Only

Hi.. first of all sorry for my bad english. Im having an issue with my 450gts graphics card, it has no display during boot but after awhile it will show display at log on screen. My os is windows xp sp3, i tested my old 8600gt it works fine at boot, but after few more trice of testing swapping my graphics card, 8600gt suddenly got the same problem. I wanted to fix this because lately i'm having my problem with o.s , i dont know if my motherboard runs fine, but i usually heard 1 beep at boot so i presume its fine.. There was a time my o.s was corrupted, and i dont know what to do cause i cant see my boot screen/post screen to see the problem, i switched to my 8600gt it display post screen but right now, 8600gt also do not display at boot, i cant even modify my bios, so when there is a problem while booting i only clear the cmos. I will appreciate any help.. Thanks..