For your Dell you need to use the "Reinstallation CD". That would partition your hard drive the way it came first from Dell, and it will install the Operating System it came with the Computer.
Floppy is a thing from the past. Installation are done today from DVD. CD's are still use as well.
The sequence for a generic installation is essentially this:
Attach the new hard drive to the computer.
Hit the key that the black screen tells you that is the set up.
That gets you into the Basic Input Output System, BIOS, for short.
There, you need to make sure what the boot up preference is, and change it to boot from CD/DVD drive, if necessary.
Save configuration and exit.
Insert Bootable media into any of the drives.
New hard drive will need to be partition before operating system is installed. Some times, the prepared installation will do it for you automatically, like the Resinstallation CD, other times as with a generic XP installation, the set up will ask you to choose and what to do.
After that, is a click and click process.
Kind of simplified but these are the steps.
The safer way is to remove any other hard drives. Windows will recognize the removed HDD once you placed back.