I have replaced the motherboard, that is the only thing, Also nothing was abnormal with the computer, only my floppy drive has stopped working. i don't think that can be the problem.
You replaced the mother board and now your floppy drive is not working. That would lead me to believe that your new mother board is having a conflict with your drivers and or your bios.

Perhaps you could reload or update your bios and check that your devices are working properly under your device manager. You might be having a problem with your ethernet connection and it is not passing data completely or allowing proper communication between devices.

Since it seemed to crash when you rebooted, it might have rolled back your drivers to a previous version that are not compatable with you current setup.

A few ideas to check anyway....good luck.