Stuck installing xp onto my eee PC.......im using a usb flash drive.?

No, it will not break your computer. You just need to reinstall of the drivers on your computer if you delete all of the partition. The reason you keep getting the error is because you already have a OS on your computer and you trying to install the same OS. Which your computer will not allow. Installing the drivers is pretty easy since you just copy the model number of your motherboard and look them up. Also your BIOS firmware have nothing to do with you installing XP on your hard drive.