Seems like W7Pro retail version runs about $140 but downloaded ISO versions are as low as $58. I want to install this on a new system with SSD drives. I see various threads about doing that (install on SSD) so my main question is about potential reinstalls and system recovery/repair. Can I just burn the ISO on a DVD and use that for install/repair/reinstall or do I need to spend the extra bucks for the retail package?