Windows 7 Enterprise won't install on T61p

Hi,
I have a weird problem maybe someone can recognize and help me out.

I have a T61P that came with vista home premium. I do not want to upgrade to windows 7, I want to do a clean install.

When I try to install with the Windows 7 enterprise DVD, I get an error, upon the start up of the installer in GUI, that a CD/DVD driver is needed or something, it's not a clear message. And the installer will not go any further.
Here's the exact verbage:
" A required CD/DVD drive device driver is missing. If you have a driver floppy disk CD, DVD or USB flash drive, please insert it now.
Note: if the windows installation media is in the CD/DVD, you can safely remove it for this step."

When I try the same with Windows 7 Ultimate, everything works without any problems

!!

I have put AHCI in compatibility in the BIOS.
I have also loaded the Matrix driver on a USB stick and tried to have the installer load it, but it said it wasn't needed

The reason I want to use enterprise is because I can get a real license through my company's MVLS for like $20 whereas the Ultimate is an MSDN license and I'm not sure when that expires.

Any ideas what this is all about?

Regards

 

Neat. I’m not sure what the issue is, but I installed Ultimate via USB memory stick (which was quite fast). If you’re interested, you might want to try this method instead.