BOOT.INI is a Hidden, Read-only file in the root directory of your boot drive, usually C:. You can access it by going to Control Panel, System, Advanced, Startup and Recovery, Settings. In the System Startup section, click the Edit button. BOOT.INI will open in Notepad. A typical BOOT.INI file, for an SP2 system looks like this:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP Profesional" /noexecute=optin /fastdetect
Ensure that the multi(0)....... line in [operating systems] doesn't wrap. If you're unsure of your setup, please post back with more information such as the number of hard disks in your system, how they're partitioned and etc.