So you need to set this in the bios before installing windows 7/ 8 normally.

I really really did not want to reinstall. Four minutes of googling has lead me to my salvation.

 

Running an SSD in IDE mode is painfully slow, about 150MB/s MAX. Around 80 / 100MB/s normally.

 

Here’s how to set your pc to AHCI mode and enjoy the full 500MB/s your ssd can push .. depending on
your purchased ssd drive. Your Mileage may very. As always backup your registry before messing with it.

 

Check it out if you would like some speed out of your expensive SSD drives.

 

Note the disclaimer. If you aren’t comfy with this sort of thing, do not attempt it.

 

http://www.ithinkdiff.com/how-to-enable-ahci-in-windows-8-after-installation/