I have windows 7 HP 64 and windows developer preview 64 in dual boot on different hard drives. After doing a pc refresh one of my drives doesn't show up in explorer. When I log onto to windows 7 all my drives show up but when I log onto window developer preview it isn't detecting the hard drive where windows 7 is installed. Any answers?

That happened during the refresh.

I can't see the drives partition that windows 7 is installed on. Oddly Windows did detect the other half of that drive which is drive (E). I tried to see if I could boot 7 without the drive WDP was installed on and 7 would not boot alone. I got an error-missing hardware screen. I have to have both drives connected in order to boot at all. I was thinking maybe if I assign a drive letter to the missing partition since there isn't one assigned, it will fix the problem. Any suggestions?

I finally figured it out after reading about windows 8's new storage space feature.

Microsoft Reveals Details About Windows 8's Storage Spaces Feature

All I had to do is reassign the drive letter in the disk management to an unassigned drive letter(M) and instantly my drive was recognized again.