so you really should ask Dell. You can't just buy any old off the shelf motherboard. Also bear in mind that when you replace the motherboard, you'll in all likelyhood have to replace the CPU. And then you'll still be stuck with XP or Vista. When all is said and done, you'd probably be better off just buying a new laptop. If you hurry, you can probably get one with Windows 7.
Do you know what an OLED TV is?
CNET explains how OLED technology differs from regular TVs, and what you need to know to make the right shopping decision.