Using comma or not before "which"

Correct... a comma is appropriate.

When, and if, you write "The latest version of Windows is 8 and is better than Version 7," then no insertion of comma is appropriate in that case.

Thanks Ragman. I also asked my colleagues and one of them answered me a comma should be used, one that she would use the comma, another one that I can use a comma if I want to, but it is not important. My colleague, who I was advising to use the comma (because I have to sign his documents) did not want to use the comma (because MS Word did not correct him!) and another colleague said that using the comma would be incorrect
Probably most people would not be bothered about that (missing) comma in a technical document, but the sentence without a comma was jumping at my eyes

Regards,
Nick

If we're voting, I vote with Ragman.

Nick you can also write "The latest version of Windows is 8, better than 7" or even "Windows 8, latest, is better than 7"