Best Of

Furmark: http://www.ozone3d.net/benchmarks/fur/

I've always used the Passmark tests.

http://www.passmark.com/products/pt.htm

If you're asking if you could revert your box to XP to get free Windows 10, the answer is no because XP is not eligible for the free upgrade. Besides, it wouldn't be an upgrade from Xubuntu anyway.

https://imgur.com/a/7jswX