If you have a Win2000, ME or 98 CD then you don't need the full version of XP ( XP upgrade actually is the full version). The XP upgrade will do a full clean install.
Go Here and download "Wipeout" unzipp and put on floppy (read the readme). Boot the floppy, at the command prompt type (without the quotes) " wipeout c: n/q n/p" Your HD will now be squeaky clean.
Pull the floppy and boot the XP upgrade CD, format the HD and when XP starts installing at some point it'll ask for the other window CD to verify the upgrade, this will not install files from the other OS. XP will tell you to pull the other CD after verification, XP installation will continue nice & clean.
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