Is the Dell XPS L702X windows 10 compatible?

Dell is not testing or developing Windows 10 drivers for this product. If you choose to upgrade, some features, applications, and connected devices may not work as expected.

http://dell.to/2eNAbBP

Its a 5+ year old laptop and Windows 10 has changed a lot of things in terms of how it deals with drivers.  You probably could get it to work, but its not 'guaranteed'.  

We updated ours without issue, but I would highly recommend the following BEFORE starting the upgrade:

1. Back up all your documents and files

2. Delete all unnecessary software, and software that you can reload later.

3. Patch/update the current version of Windows you are upgrading from so that it's current.

4. Update the BIOS and all drivers to the most recent stable version (from Dell)

Then, I would use the Windows Media Creation tool to create a bootable USB installation drive, and load the current drivers for the pre-install version of Windows as a backup.

I would then try the "in place" upgrade, assuming you don't want to change any settings.  However, if I ran into any difficulties with that, I would install from the USB drive using the media created above.