New
#171
Sounds like the baseline chipset driver decided to not be happy with it. As Greg pointed out, download the Vista x32/64 (Depending on which install you did) driver and install that, repeat the backup process and see if that has improved. I would also note the chipset Dell says it is for their driver, and possibly look and see if there is a Win 7 Driver out there from the manufacturer. Dell tends to gravitate towards Intel or nVidia based bored. Since it was mentioned intel, more than likely, see if you can find the intel drivers from intel for that particular model, but again, verify the chipset for your model and get accordingly if the ones Dell has doesn't work as nicely.
Worse case scenario, depending on how old that XPS system is, it might be a faulty board given your previous mention of having problems with it with Vista prior to all of this. Not knowing the full history, can't be sure.