From what I can make out of your post, and I realise that English might not be your primary language, is that you seem to be trying everything at once.........
One thing at a time, let it FINISH, before you start part next.
If it helps, write down what you want to do, and the order you want to do it in.
As for the dual boot question. Install the earlier Windows OS FIRST.
Remember : NTFS file system OS's can 'see' FAT systems, but FAT cannot 'see' NTFS.
98 - ME - 2000 - XP
Get yourself a copy of 'Partition Magic' to sort out what partitions go where.
And get them to buy a NEW HDD, AND some extra memory [128 MB more at least]
