From an Ebuyer specification for a Lenovo laptop:
Lenovo B50-45 Laptop:
Technical Specifications
General
Product Type Notebook
Operating System Microsoft Windows 7 Professional 64-bit Edition / Windows 8.1 Pro 64-bit Edition downgrade
Processor / Chipset
Made me chuckle. 
have you tried 10 yet?
No I haven’t. Is it any good? Do they still insist you buy a new licence key for upgrading your computer?
10 isn’t out yet, except as a free preview. It’s basically 8 but with something resembling a start menu back again. I’m sure there’s more stuff but that’s what it behaves like in practice. Basically I’m about as happy with using it as I am with 7, with the caution I haven’t really pushed it. I’m running it on a couple of crunchers since they were still on XP and some projects get a nice boost from 64-bit goodness.
Ran 10 for a little bit, yet way to many issues with programs; well frankly wasn’t impressed enough to fight my way through the problems. Think I’ll wait till win 10 is ready.