Aye, I'm trying to get a genuine Dell image. I did find one available which requires a dual layer DVD so haven't burnt it yet. Unless anybody knows how to trigger a network install using an iso?
I'm also trying to get an official Dell disc from Dell.
You can put it on a USB memory stick. Here is what I do (this is all from memory so there may be a mistake or two but I've done this a lot recently so should be ok

)
Insert a memory stick with enough space.
Open the run box and enter
diskpart. Press OK.
When it loads, type
list disk.
Choose the number of your disk that corresponds to your memory stick size e.g
select disk 1
Type
clean to erase the memory stick.
Type
create partition primary to create a new primary partition on the USB memory stick.
Type
active to mark the partition as active.
Type
format fs=NTFS quick to format the memory stick to NTFS.
Type
assign to assign a drive letter to the memory stick.
Close diskpart.
Extract the disk image that you have into a folder.
Load up command prompt and change the directory to the folder of the disk image (e.g
cd C:\DELLIMAGE\).
Change the directory to the sources folder within it by typing
cd sources
Type
BOOTSECT /nt60 X: (X being the drive letter that was assigned to your memory stick with diskpart.)
Close command prompt, and copy all of the files in the disk image folder to the memory stick.
Boot up machine and set it to boot from the memory stick and you should be able to install from it. Sorry if this is badly written but I've only written it quickly
(This will work for all Windows Vista/7 install media)