You should not change IDE to SATA. That is the type of hard drive that is actually installed on your computer and cannot be misidentified in the bios. Change it back if you have an IDE hard drive and reboot to the Windows 7 disk and install the new OS. You should run the Windows Upgrade Advisor first to make sure your hardware can handle Win 7. That will tell you what hardware or software needs to be upgraded or removed before the install. Windows 7 info HERE.

Thanks for your reply.

My current installed Windows shows me as a harddisk a: ST9160823ASG, which is a Seagate Momentus 7200.2 and this harddisk has a SATA-II interface.

Why should I run this harddisk in the slower ATA mode if it is a SATA-II disk ?

There must be a way to either change it in the BIOS or provide a SATA driver for Windows

The same issue exhists with XP.

You need F6 drivers to install AHCI disk mode.

There are ways of installing the AHCI drivers then removing the ATA drivers.

http://support.microsoft.com/kb/922976

Error message when you start a Windows 7 or Windows Vista-based ...

Error message when you start a Windows 7 or Windows Vista-based computer after you change the SATA mode of the boot drive: "STOP 0x0000007B INACCESSABLE_BOOT_DEVICE"

To resolve this issue automatically, click the Fix this problem link. Then, click Run in the File Download dialog box and follow the steps in this wizard.

Thanks a lot for the answer.

It worked PERFECT !!

It is very poor from DELL that they deliver the devices with settings which do not allow best performance.

And it is even worst that there is nothing to find on their support page

Anyway - Problem solved

Thanks a lot!