I want debian as dual boot with my windows vista, Free'd up 50GB in my d drive. Plan to use 40 for debian install, 6GB for swap space

Have a 16GB USB drive

Downloaded http://unetbootin.sourceforge.net/

Downloaded DVD files of stable debian-7.0.0-amd64-DVD-1.iso ( debian-7.0.0-amd64-DVD-2.iso and 3)

After I choose HD install, unetbootin says place the ISO in the same place. but I have 3. do i need to merge them? if so any freeware to do that? can i do it with 7zip? when I extract with 7 zip there are classes between the 3 ISO files. Just over write? Options to merge (format etc for 7zip) ? Or I must use

I tried to keep the 3 files with the other unetbootin files but get an error msg Files I have on my USB

06/30/2013  11:44 PM         2,835,648 ubnkern
06/05/2013  12:14 AM     3,998,007,296 debian-7.0.0-amd64-DVD-1.iso
06/04/2013  03:30 PM     4,696,872,960 debian-7.0.0-amd64-DVD-2.iso
06/05/2013  01:25 AM     4,698,955,776 debian-7.0.0-amd64-DVD-3.iso
06/30/2013  11:45 PM         6,530,278 ubninit
06/30/2013  11:46 PM               155 syslinux.cfg
06/30/2013  11:46 PM            60,928 menu.c32

also i can only copy above files if i format my USB as NTFS

On FAT32 says too large to copy .iso

How do I get around that? My internet needs a login so cannot do net install