Where can I download a Windows 7 ISO image?

http://www.microsoftstore.com/store/msstore/list/categoryID.50726100?WT.mc_id=po intitsem_US_Google_5-Windows7_generic_2&wt.term=windows%207%20microsoft&wt.campa ign=*5+-+Windows+7&wt.content=UjMUpHzE&wt.source=google&wt.medium=cpc&WT.srch=1

The real trick usually after you have Windows ISO is to make sure if you burn it to DVD to do so at the slowest burn speed or the install will mess up.

You can also pick up a single-computer System Builder edition for $99 Home Premium 64-bit (it comes in only 32 or 64, not both like retail) and while you can reinstall multiple times, you can't install on another computer later than the one it was origiinally.