Switching from IDE mode to AHCI help needed, please

I have an older win7 media server (WMC with 4 cable card tuners) that I want to add a 3TB drive.
However when I first installed sata controller was set to ide mode.
The 3tb drive only works with AHCI mode and of course my WIN7 will not boot
if I only switch mode in bios.
I was going to save everything on WHS2011, switch mode then restore everything
but system drive and storage drive GB usage is larger than what I have on WHS.
I was thinking of saving my storage files on other computers but that will take forever.

Any suggestions?
Thanks,
Ray

I need to re-format/re-install win7 anyway. I guess I will save storage drive on whs then install win7 again with AHCI turned on.
Are drives written to differently with / without ahci enabled in bios??
are data drives swappable?? Or I can only read a AHCI drive in an AHCI enabled system??
Thanks,
Ray

OK, I did a new install of win7 64bit with AHCI enabled in Bios.
After completing updates and all I installed the Seagate 3TB drive.
Had to run Seagate DiscWizard to be able to have access to more than 760gb
I picked MBR scheme because motherboad does not support EFI.
No problem for 2TB and 800GB drives.
BUT................................
Can I delete Seagate DiscWizard for computer?
WILL backup-restore in win7 still work? (will repair disc read backup stored in 760GB drive of 3TB drive?)
If I backup to WHS2003 or WHS2011, will I be able to restore AHCI drives?
Thanks for any help
Ray

Did you check for a newer BIOS update that might handle larger drives.

Another option is using GPT formatting which is ideal for the larger drives: Convert MBR Disk to GPT Disk - Windows 7 Forums. You don't need an MBR on the disk if there's no OS.

Then you wouldn't have to worry about uninstalling Disk Wizard. Have you read it's Manual?

Thank for help.
Here is my outcome:
First mother board is older. GA-MA74GM-S2 Rev 4.3
Was able to use formated 3TB drive (GPT) IF I enable AHCI in bios
Was NOT able to backup/restore in whs2003 or whs2011 (restore disk or USB drive never worked)
Was able to do win7's backup/restore IF I used a IDE cd-rom drive (not a sata)
Ray

What type of backup do you have, and want to do?

The best and safest way to back up is drag the data to external, another HD. You can save a backup image using Win7 backup imaging or a 3rd party app like free Macrium: Backup Complete Computer - Create an Image Backup
Macrium - Image your system

wanted to use WHS2003 or WHS2011
but settled on win7's backup/restore.
Can save on lan as well.
motherboard just too old. but still can backup other ways.
Thanks,
Ray