Is there a Difference between the DELL WINDOWS 7 OEM EULA and the MICROSOFT WINDOWS 7 OEM EULA?

There are two types of OEM licensing:

Royalty OEM - which refers to major brand companies like DELL, HP, Lenovo, Sony, Acer and others who sign a contract with Microsoft Licensing to receive access to the Gold Master build of Windows 7. This type of license restricts the software only to that branded computer.

System Builder OEM - this is another type of license which is used by Professional System Builders. OEM licenses are to be installed by professional system manufacturers only. Under Microsoft's OEM License Agreement, they are not to be sold to end-users under any circumstance, and are to be preinstalled on a computer using the OEM Preinstallation Kit (OPK) before shipment to the customer, and must include at the very least the manufacturer's support contact information. They are, therefore, designed for installation only on a single computer and are not transferable, even if the original computer is no longer in use. This is not usually an issue for users who purchase new computer systems, because most pre-assembled systems ship with a preinstalled operating system. There are few circumstances where Microsoft will allow the transfer of an OEM license from one non-functioning system to another, but the OEM System Builder License Agreement (SBLA), as well as the OEM End User License Agreement (EULA) do not contain any allowance for this, so it is entirely up to Microsoft's discretion, depending on the situation

http://www.microsoft.com/oem/en/licensing/sblicensing/pages/licensing_for_hobbyists.aspx

Some Royalty OEM's permit virtualization of their Windows 7 OEM licenses as its only in use once on the same machine. So for instance, say your computer came with Windows 7 Home Premium on a new DELL. You could replace the installation on the physical hardware with Ubuntu Linux or another editions of Windows 7 and run the Home Premium license in Virtual Box and activate it.

Quote from the Windows 7 EULA:

d.    Use with Virtualization Technologies. Instead of using the software directly on the licensed computer, you may install and use the software within only one virtual (or otherwise emulated) hardware system on the licensed computer. When used in a virtualized environment, content protected by digital rights management technology, BitLocker or any full volume disk drive encryption technology may not be as secure as protected content not in a virtualized environment. You should comply with all domestic and international laws that apply to such protected content.