I got an XPS 15 3 years ago. I think it had Windows 7 at the time so I've had it install every upgrade from Windows 8 to Windows 10.
Lately it's become ridiculously slow - taking 30 seconds or more to open a small folder even though it has SSD, lots of ram, and I'm barely running anything most of the time. There is clearly some kind of configuration problem that got messed up over time.
I'd like to re-install Windows but I'm not sure what will happen. Will it install Windows 7 from the original image? Will that upgrade to Windows 10 directly? Is that still free?
After 30 days with Windows 10 installed you cannot restore usiung the restore feature in Windows. You will need to format and reinstall Windows 7 manualy. Click the link below for information to install Windows 7.
How to: Reinstall or Restore your original Windows installation after upgrading to or evaluating Windows 10
After the initial upgrade from Windows 7 OEM/Windows 8 Retail to Windows 10 your systems hardware profile was submitted and registered with a Microsoft Product Activation Server. You may clean install Windows 10 at any time and your system will automatically reactivate when online provided you install the correct Edition.
Direct clean installation of Windows 10 RS1 (opposed to a series of upgrade installs from a factory image) will result in optimal performance. For more details see: