If you would like to check inside the registry to make sure it is running in AHCI mode you can do that too. Here are the steps(applies to win7 since i'm unsure of how w8 will work with it, may be why it doesn't display AHCI in device manager for you?)
1.Exit all Windows-based programs.
2.Click Start, type regedit in the Start Search box, and then press ENTER.
3.If you receive the User Account Control dialog box, click Continue.
4.Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Msahci
5.In the right pane, right-click Start in the Name column, and then click Modify.
6.In the Value data box, type 0, and then click OK(if it is already 0 then read my very last line).
7.On the File menu, click Exit to close Registry Editor.
After that you would need to reboot and go into bios and enable AHCI. When you log back into windows it should automatically start downloading the AHCI drivers.
If the value is already set to 0 then it is currently running in AHCI mode so no need to continue