Strange problem fter installing windows

Hey guys I'm new here and this is a first for me when it comes to a problem like this.

The break down of it all is I just built a new system and after installing windows and having it up and running, I go to restart and when I do with the DISC not in the drive I get a DISK BOOT FAILURE error. However I read up to do the FIXBOOT command in windows repair. Windows said it has fixed the boot record but no matter what I try I cannot get it to boot with out the CD in the tray.

The windows version I used was XP service pack 3 and I also tried an old RC build of Windows 7 and got the same error.

Another thing is I have this exact same thing happening with another PC I also built today.

Spec for the 1st pc are:

Core i7 920
ATI 4890
3 Sata Hard drives 500GB, 160GB and 250 GB
EVGA X58 SLI LE
OCZ Platinum DDR3 1600
Corsair 750 watt

2nd PC
Phenom II 720
GIGABYTE GA-MA790GP-UD4H
4 GB Patriot Hyper X ddr2 800
80 GB ide Drive and 500 GB WD Caviar Blue
Corsair 550 Watt
ATI 4870

Same exact problem on both PCs and ever part seems to be working fine. And i already went over the bios options to make sure the boot device priorities are not messed up causing this to happen.

Thanks.

Tried fdisk /mbr ??

Thanks for the reply guys but I figured out the problem, seems it was my own stupidity causeing the problem on both systems. I did not set the 1st boot to Hard Drive... go figure. All Is well now for the moment