Lets be frank here, they don't work perfectly well. There's still a lot of compatibility issues going from XP to Vista/7.
The point is XP is still a lot better for netbooks than 7. XP is 7 or 8 years old at this point. Ubuntu or Mint is less bloated still and are actually modern OSes.
My NC10 running Windows 7 works perfectly thank you very much. I am also aware of a large number of members of this forum that run Windows on a netbook with no problems or performance deficit.
May I suggest that if you have a different experience that you hadn't built the machine properly?