Computer doesn't boot XP on start but on restart it does

[Billj12901]

I just built a computer, an ASUS board P4S800, Pentium 4 2.8gHz, WD80gb HD,512mb RAM, Lite on Combo drive, Antec Case, ATI Radeon 9600, 56k modem. Ok the computer works great with one glitch, from a cold start it goes through post and looks like it will start up but then says insert boot disk or modify boot settings. I can restart it and Windows XP will then be booted and everything is fine. I believe this could have happened with the installation of the modem but still I am not sure and have tried changing bios boot preferences. This has no bearing because whatever I put, restore default, etc. the restart causes XP to load fine. Please, if anyone could contribute I would appreciate.

[Billj12901]

I am also getting a overclock error from some cold boots but most of the time it says 'insert bootable disk or restart to boot' So I am still trying to work this out so please drop a line with some thoughts

[Billj12901]

Another update, I took out modem and software for said modem and tried again but no problem. Found a system error with the raid drivers but just loaded the drivers for the raid software and that conflict was gone. I am not sure what repair command I should try with windows xp pro, If i should use bootfix or something else. My only other recourse before tearing down and rebuilding is to reload Windows XP Pro completely which would not be that difficult. Please give me some idea, since I believe I am doing this by the book, is there anything I am missing.