The Windows 7 .iso will take a long time, the IE8 file should be quick.
If using the Windows 7 .iso file see my wiki Windows Reinstallation guide/A Clean Install of Windows 7:
http://en.community.dell.com/support-forums/software-os/f/3524/t/19480753.aspx
Page 272 to download and create the media and then Page 64 to install Windows 7.