said by Guspaz:
If you want to keep a familiar user experience kind of like windows, but still want to stick to Ubuntu (because it's the most popular and has the best support from third party companies like Valve), you can try Kubuntu (KDE), Xubuntu (Xfce), or Lubuntu (LXDE). That is actually in order of how "lightweight" they are. KDE is a full-featured but heavyweight desktop environment, Xfce is traditionally a lightweight environment that is cleaner and less complicated than KDE, while LXDE is newer and has slightly lower memory usage than Xfce.
They're pretty close though. In mid 2011, Phoronix tested RAM usage, and came up with these averages in their test:
KDE 4.4: 522 MB
GNOME 2: 400 MB
Xfce 4.6: 342 MB
LXDE 0.5: 311 MB
If I had to pick a desktop Linux distro to install today, it would either be Xubuntu 12.10 or Mint 14.1.
I've been pretty impressed by Mint. Good choice here, then again all of which Gus suggested is good