I made a boot-floppy for WinXP the way you are supposed to (rt-click floppy drive in My Computer, choose format, choose Make Boot Disk), but when I try to boot with it if I try to switch to the hard drive (c:) it says something like "Invalid drive". Can anyone help? I tried using one floppy I have (I think it's some kind of boot floppy or virus-recovery boot-floppy for Win98 SE, which is on my other computer) and it printed a message saying that some viruses can cause a floppy to not recognize a hard drive...

I think this is the boot disk you want: HOW TO: Create a Boot Disk for an NTFS or FAT Partition in Windows XP http://support.microsoft.com/default.aspx?scid=kb;en-us;305595

That starts up Windows XP on the hard drive, but that's not what I want to do. I want to just have DOS running from the floppy, but able to recognize the harddrive (c:) so I can switch to c: and delete a 500MB file that XP isn't allowing me to delete because it says it is always being used by another user or process (which can't be right). Isn't that what an MS-DOS startup disk should do (just stay in DOS). This is the option in MyComputer-RtClickOnFloppyDrive-Format-MakeDOSstartDisk, but when I boot with that and try to switch to the hard drive it says "Invalid drive specification".