Windows XP downgrade restore on a Dell Precision M2400 laptop

Hello,

I have have a Dell Precision M2400 laptop with the Windows XP downgrade option and I want to restore Windows XP to its initial state for some reasons.

I haven't received any Windows XP Restore disk so I start some investigations on the web.
I have read this on the Dell support website to access to the restore process:
* For systems with Windows XP:
"When the Dell splash screen appears during the computer startup process, press and hold and then press . Then, release both keys at the same time..."
* For systems with Windows Vista:
"As the computer starts, press on the keyboard until the Advanced Boot Options menu appears on the screen. Press the on the keyboard to select Repair Your Computer on the Advanced Boot Options menu, and then press ..."

Both of these procedures gives nothing:
* the procedure don't do anything
* the procedure displays the advanced boot options but there was no one to restore the system because I was not using Windows Vista but my Windows XP downgrade

It seems that the keys combination should be handled by the MBR boot code (Dell customised) to boot to the DSR (Dell System Restore) partition. So, first of all, I want to know if my laptop (Dell Precision M2400) has a DSR partition that should be accessible via .

Next if it has a DSR partition, I must understand why I cannot access it. But for that I have an idea. Because I use a boot manager (Grub) for Windows XP/GNU Linux Ubuntu dual boot, I think that grub can have overriden the Dell MBR boot code by its own. So in this case the second question will be how to restore the Dell customised MBR.

Thanks in advance for your answers.