I just discovered a good, clean source from where you can download a Vista ISO. You need to have your product key (e.g. from the COA sticker on your PC).
Vista ISO - Download and Create Installation DVD or USB
The above link is currently back working so you should follow the instructions, in the linked Tutorial.
If this source should go offline again ....
Downloads are still possible
Please post your request at the end of this thread Stating whether you require 32 or 64 bit and include a suitably disguised email address where a link may be sent, [ in the form Someone at some address dot com
You are strongly advised to edit your post to remove even this disguised address After you have received the link .