To the best of my knowledge, some motherboards will request the fan to spin for a few seconds upon startup as test, that maybe your issue in this case.
Download a legal copy of the Windows 7 installation DVD with SP1 integrated from here: Official Windows 7 SP1 ISO from Digital River
Make sure you get the same version you have, Home Premium, Pro or Ultimate and 32 or 64 bit. Note that Basic or Starter is not available.
I recommend using ImgBurn
at 4X speed (or the slowest available) to create the DVD from the downloaded .iso file.
You can do this on any computer capable of burning a DVD, family member, friend, etc.
For techies or folks who work on computers: Create Windows 7 Universal ISO With All Editions Selection On Install with ei.cfg Removal Utility
This will fit on a 6GB flash drive or can be burned to a DVD.
Try booting from it by selecting the USB/CD/DVD as the first boot device. If it boots, it's a Windows problem and not your PSU.