OS Memory Requirements

OS

Required / Realistic

Ubuntu (full Gnome)

384 MB / 512 MB

Xubuntu

192 MB / 256 MB

Windows XP

64 MB / 128 MB

Windows Vista Home Basic

512 MB

Windows Vista (Other)

1 GB

Windows 7 32 bit

1 GB

Windows 7 64 bit

2 GB

Win 7 requirements http://www.microsoft.com/windows/windows-7/get/system-requirements.aspx
Win xp requirements http://support.microsoft.com/kb/314865
Ubuntu requirements https://help.ubuntu.com/community/Installation/SystemRequirements
Win Vista requirements http://www.microsoft.com/windows/windows-vista/get/system-requirements.aspx