You'll have to check at your Lenovo's website, to find out if they support the Core2Quads. Sometimes a quick BIOS upgrade is all that maybe required. But if your mobo cannot support 95W CPU's then tough luck. Also, Core2Quad are ridiculously expensive these days, so unless your getting it second hand for like $80 or less, it wouldn't be worth buying.
The best thing for you to do, is sell off your current rig, and build a new one from scratch. If your a bit tight on money, even a $140 FX-6300 will be a massive improvement over your older dual cores when it comes to video encoding. AMD's new FX chips just LOVE video encoding:) You get almost the same performance from a $190 FX-8350, as a $330 Intel i7-3770k !!! http://www.tomshardware.com/reviews/fx-8350-vishera-review,3328-12.html
If you have money to spare, get an FX-8350 or if you have loads of money, an Intel i7-3930K is definitely the beast for you (6C/12T) .
Edit - Forgot to add, OEM windows versions are tied to your motherboard, not your CPU, so incase you do an upgrade, you should be fine