When you say you've formatted it, do you mean when you're installing Windows, and it asks if you want to do a quick format?
If so, this probably will leave files as it is only a quick format to allow Windows to install, so basically only deleting the things it needs to.
The best thing you can do is insert a boot disc at start-up (You can make them using Add/Remove Programs, under Boot disc, unless it is Windows XP which i have a feeling it is, and in this case you can go to this:
Just look for creating an XP start-up cassette, and you're version.
You could use the XP cd as a boot to it as well, yet I have not used that way, (just make sure in you're bios, it is set to check floppy/cd first, before the hard drive!)
Finally just type after putting it in, and it lets you type:
cd:\ (to step the computer away from looking at the floppy)
and follow the instructions
Hope this helps