According to the Microsoft Support Article ID: 916196, only certain USB floppy disk drives are verified to support for use during Windows XP installation. You may refer to the following model list from Microsoft:

1. Mitsumi
2. Y-E Data
3. Sony part number 09K9835
4. TEAC
5. IBM option part number 27L4226, FRU 05K9283

For more details, please refer to:
Microsoft Support: click here 
Intel Rapid Storage Technology: click here
 
If your USB floppy disk drive is listed above, you may follow the instruction below:

1. Go to BIOS setting and find [Standard CMOS Features], set [Drive A] to[None].
2. Select [Integrated Peripherals], and [Enabled] [USB Storage Function].