You won't be able to tell the difference. You can't move to AHCI without making changes to the registry or reinstalling Windows 7.
You should be able to notice the difference, but you'll have to try one of the following to get it to work:
Make a backup of your registry file before attempting any of the following!!
Try the suggestion from this link first:http://www.tomshardware.com/forum/275009-31-ahci-sata-drives
If the suggestion from JamesA57 doesn't work, then try this one:http://forums.pcper.com/showthread.php?t=444831
If either of the above mods don't work, try this one (it's more complicated):http://forum.msi.com.tw/index.php?topic=106575.0
Search Google for the advantage of AHCI over IDE mode. There are plenty of links you can browse to offering fixes for this issue.