Installing Win7 on a HDD setup for IDE mode in AHCI mode

[videobruce]

I'm not sure where to put this, but here it is.

Using a already formatted & partitioned HDD from a older non GPT ready (if you will) MB, I want to install Win7 64 bit using AHCI. The current O/S on that active partition is XP which I want to replace.
The other partitions (two) have data on them that I don't want to loose. (I do have it backed up).

What happens to the drive when I install Win7 in AHCI mode to the other non active partitions?

 

[videobruce]

A 2nd question; with a SSD drive that I have installed Win7 on (fresh install), for kicks & giggles, I switched back to IDE mode and booted back into Windows. To mu partial surprise, there was no difference unlike the other way around where you get greeted with a BSOD.

With that SSD, if I leave the SATA mode to IDE, what is the disadvantage?

 

[Kursah]

ACHI is just allowing some extra features for OS utilization of the drive and how it assigns writes and reads using NCQ and such from my understanding, you won't lose your other data. It's supposedly a little faster and better so just stick with ACHI.

You should have the SSD in ACHI mode because ACHI has features that can actually help benefit OS speed and snappiness under operation. Take a quick google search and you'll find a ton of articles out there about it.

It is pretty easy to switch Windows 7 form IDE to ACHI if you're getting BSOD's going back to ACHI, I don't have the link handy at this very second but again a quick google search and I'm pretty sure it's a quick setting...ah heck let me go look..

Convert from IDE to AHCI

Open Registry Editor and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci.

Right click on the Start registry DWORD and select Modify.

Set the value to 0 and click OK.

Now the Start setting should be set to 0.

Reboot and enable the AHCI setting in your BIOS.

Source: http://www.tomshardware.com/forum/307293-30-ahci-wihtout-reinstalling-windows

 

[videobruce]

I wasn't planning on leaving it to IDE, I was just wondering where I would see a difference since I wasn't sure it would work going from AHCI to IDE. How about GPT vs MBR when Windows is installed? Wouldn't that affect the other non active partitions?

Lastly, how about "compatibility mode. Why would I want to turn it off?