You shouldn't have any problems upgrading to Win 7 32, I don't know about 64 bit. I did check the Dell site and they don't support that model with Win 7, but do some googling, other peeps have done it.
If you read this guy's story, and the replies he gets too, you'll see that the job can get tricky.
I've a few hints. . .
Download a Windows 7 .ISO from Microsoft and burn a DVD.
Use this DVD to install Windows 7 to a Virtual Hard Disk. (VHD) DON'T activate it or use your Product Key. You have 30 days to experiment without activation. This should be plenty of time.
Experiment with this system and see if you can overcome all the obstacles satisfactorily. This will give you your answer.
Note: You'll have FAR FEWER issues if you choose 32-Bit Windows 7. Not only is it more compatible with almost everything out there, it's more likely to "play nice" with stuff left over from your current system.
When it comes time to install new drivers, check Dell for the proper order for their installation. This seems critical. When I'm doing this, I rename the drivers with a prefix: A_, B_, C_, etc. That way, I just need to install them in alphabetical order.
Cheers, PW.
P.S. On every site where I checked the system requirements for Windows 7, they did't mention ACPI (Advanced Configuration and Power Interface.) Windows 7 will NOT run on a system without ACPI.
Since Dell lists ACPI drivers for your XPS 720, I assume your system is ACPI compliant.
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