Yep, you should have said no to converting it to dynamic. If you have not already, you should create a set of factory recovery DVDs, or saving recovery image to USB to be safe. This way you can use it to do a factory recovery of Windows 7 if something should go wrong converting the HDD back to basic.
HP PCs - Creating Recovery Discs or Saving a Recovery Image to a USB Flash Drive (Windows 7) - c01867124 - HP Business Support Center
Next, backup anything that you do not want to lose to be safe.
Afterwards, use OPTION FOUR in the tutorial below to convert the entire disk back to basic.
Convert a Dynamic Disk to a Basic Disk
When everthing is back to how it was, then you could use METHOD TWO in the tutorial below to create a new extended logical partition to use to install Windows 8 on for dual booting with your Windows 7.
Partition / Extended : Logical DrivesDual Boot Installation - Windows 8 and Windows 7 or Vista