Cheapest way to upgrade to Windows 10?

[agnes]

I've got a paticular version of Windows 7 which won't allow me to cleanly upgrade to Windows 10. As such, I'm able to format and install what ever OS allows the cheapest upgrade.

Any suggestions? We are about to roll it out at work and I need to familiarise my self with it.

 

[cadmunkey]

Check out key sites like Kinguin. Can get OEM versions for very cheap monies.