MY HP PAVALION WILL NOT BOOT WINDOWS?

My Hp froze up so i powered down and then powered it back up and when I did that it will no longer boot windows. I get the screen telling the computer was not shut down properly and gives me choices on how to restart ie in safe mode , last known configuration that worked. And nothing worked. I hit f1 to enter setup and looked at the drives and it shows only my external maxtor as my primary drive what makes no sense to me is that It's unplugged but still show s as primary drive. Any suggestions would be greatly appreciated