Make sure your boot.ini files has only these lines in there.
copy and paste the boot.ini lines mentioned by zipp51.
[boot loader]
timeout=10
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect"

Also right click My Computer and select Properties.
Click the Advanced tab.
Under Startup And Recovery, click Settings.
Under Default Operating System, the drop-down list displays the current boot system.
Select the Windows XP OS from the list
Deselect the option Time To Display List Of Operating Systems.
Click OK.Restart
Make sure you don't have any media in your drives and try resettings the bios back to defaults...Why not try everything