Invalid partition table on USB drive ?????

Hp p2-1134

OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: AMD E-450 APU with Radeon(tm) HD Graphics, AMD64 Family 20 Model 2 Stepping 0
Processor Count: 2
RAM: 3686 Mb
Graphics Card: AMD Radeon HD 6320 Graphics, 384 Mb
Hard Drives: C: Total - 465640 MB, Free - 341102 MB; D: Total - 11196 MB, Free - 1374 MB; G: Total - 953867 MB, Free - 50255 MB; I: Total - 953835 MB, Free - 814876 MB; L: Total - 152617 MB, Free - 151429 MB; O: Total - 953667 MB, Free - 373523 MB;
Motherboard: PEGATRON CORPORATION, 2AD1
Antivirus: avast! Antivirus, Updated and Enabled

I have what I think is a usual “Invalid partition table” problem.
The other day we had a “power glitch”. When I rebooted after it…I got “invalid partition table” after the boot screen. The next day I borrowed a friend’s machine and looked it up. What I found said unplug all USB devices (except mouse and keyboard).
Then reboot when the boot screen finishes press f8 and get to the recovery menu.
I did that. However I was not quick enough to press f8 instead of recovery menu I got system information. Then it booted into Windows with no problems.
With further investigation I discovered that it would boot into windows as long as the USB devices were unplugged. But once windows started I could plug the devices back in with no porblem
I know this is not normal but my question is is the problem in the HD or the US drives