What do you mean boot from a floppy? just put a floppy
disk in the drive and start the computer?
You may have first to hit the appropriate hot key (often DEL or F1 or
F2) as the initial power on memory count happens, so as to get the BIOS
setup, then set the Boot Order to be A:, then C:, then CDRom in the
BIOS Setup page (or adjust in the Boot page if there is one). Then have
the floppy concerned in the drive and Exit saving settings.
For repair of XP, set normally CD first, have the XP CD in the drive and
boot that.
Either
Enter Setup, and after the license agreement take New Install. When it
asks you to confirm where, hit ESC; select and delete the current
partition and make a new RAW one to be formatted at the next stage
The important point is the delete. Without that it will just go ahead
and make a new install over the top of the old one
Or instead of New INstall, take Repair Installation
This will retain your existing software installations and most
settings. But Updates will have to be run again, especially SP1;
It is important to activate the basic XP Firewall before you ever
connect to the net to get the patches, so as to be protected against
things like the BLAST worm.