I was recently using my Gateway desktop and the power in the whole house went out for about 10 seconds. I left the PC off for about 10 mins but when I turned it on, the light on the power button fades in and out constantly like it's hibernating or something. But it still boots up and loads Windows 7 fine. Except all USB peripherals and PCI wireless card have no power. Same thing happens in safe mode. But they do work outside of the OS (like I can use the keyboard to enter the bios but once Windows loads, the keyboard turns off).
Maybe Windows got corrupted from the sudden shutdown, try doing a windows repair using your windows disk.
I tried it but it didn't detect anything wrong. I can boot up into Windows and get to the desktop and everything seems to work, it's just usb devices and the PCI wireless card. The same hardware works fine outside of this current installation of Windows so I'm almost certain its a software problem.
In that case it must be that some files have got corrupted. I'd be inclined to back up your data and reinstall the OS. It's a bit of a cop-out, but probably easier in the long run. Who knows what more subtle problems there might be?