Well for a start and depending on your system setup, you often need two files on the floppy, called Winnt.bat and Winnt.sif. Sometimes you can get away with just Winnt.sif, sometimes not.
I normally create a new Windows CDROM with the necesary files burned into its i386 folder for unattended installs.
If the floppy is not being autodetected, you may have to start the installation manually using a couple of switches:
1. Copy SMARTDRV.EXE from the Windows CDROM onto a Windows 98 boot floppy.
2. Boot from the Windows startup floppy
3. SYS C: just to make certain the drive is bootable
4. start SMARTDRV.EXE from the command line
3. Change directory to the i386 folder on the Windows 2000 CDROM
3. Start the instalation using winnt.exe for a clean install or winnt32.exe for an upgrade install followed by the /u switch and the path to the answer file, like this:
WINNT32 /unattend:"answer_file_name" /s:"path_to_installation_files"
Change the drivepath and filename to suit.
I realise that this defeats the purpose of an unattended install, but often they go wrong because of hardware on a certain system that just does not want to play ball.
The most reliable unattended installs in my experience are where you build a new Windows CDROM with the answerfile incorporated into the disk, or where you run the install over a network.
Diagnosing why it went wrong for you and your PC is impossible without access to the system.