I recommend you put a SSD into that laptop 🙂 before continuing.
What you do is: You get another computer / laptop capable of burning DVDs:
http://cdimage.debian.org/debian-cd/8.3.0/amd64/iso-cd/debian-8.3.0-amd64-netinst.iso (brasero did that nicely on a DVD-R, the dell would not take accept CD-R „selecting boot device failed“)
Hit F12 during boot and select your DVD-Drive.
You should see all the normal „Language – Region“ stuff.
Then the Wifi missing firmware iwlwifi-6000-4.ucode popup comes:
What you do is you download this *.deb
and place it on a FAT32-USB Stick.
Attach it to your laptop, wair 3 seconds, hit enter … and it should continue without error.
PS: I Stick to ext3 for the next 5 years until ext4 is stable.