Can you simply click Next anyway, despite the  message?  If not: Boot to the Windows 8 DVD, instead of Install Now, click on Repair Your Computer, Advanced Options, Command Prompt ... when it opens, type in the following: diskpartselect disk 0clean Then, attempt to install. The above will remove all partition and disk information, allowing you to do a clean install to an empty disk (those partitions are not necessary, and Windows will create its own partitions (two) that it needs to install and run). 
I got the replacement hard drive from Dell that I was told would come with Windows 8 and drivers preinstalled. Well I installed the hard drive and it tells me that NO OS can be found. I didn't have a chance to make backup discs of my own but Dell sent a Windows 8 Recovery Media CD with the laptop and now with the replacement hard drive.When trying to install Windows 8 onto the new hard drive I get to the part where it tells me to choose a partition to install Windows 8 on and none of them will let me. There are 5 to choose from and I don't know what to do to get past this. The biggest partition which is 5 has about 934GB of space left out of 1TB but as I mentioned I can't choose it or any of the other ones for installation.
Can't Install Windows 8 on Replacement Hard Drive