I was customize my computer on cyberpower pc http://www.cyberpowerpc.com/system/Mega_Special_III
But when I look at the operating system it said either windows 7 or format hard drive only so I'm kinda confuse on that. Can someone please help me sort this out and tell me what format hard drive only and windows 7 do exactly because its $100 for windows 7 for my computer or format hard drive only.
What the spec sheet says is that the hard drive has been formatted, but no operating system is supplied as part of your purchase.
You needed to choose one the options for Windows 7, Home Premium, Business or Ultimate at additional cost which is dependant on your choice.
By not selecting one of the options starting at $104 for the Home Premium, you are without an operating system and will need to purchase one before you can use your pc. There is no way around this you just have to pay for it.
Follow the link you provided and click on Summerise, a new window will pop up, scroll down the list and you will see "Operating System" - None, formatted hard drive.