Pay careful attention during this step if your system uses a boot partition, uses multiple OS (more than 2), or chainloads bootloaders.
For systems with such a boot partition, it is best not to overwrite the MBR.
Ubuntu Maverick Meerkat runs well with as little as 384 Mb RAM.
The installation takes between 3-4 Gb hard drive space, and 8 - 10 Gb will be needed to run comfortably.
(However, at least 25-30 Gb will likely be needed for routine usage.) If you have an older computer with less memory than this, consider Lubuntu (if 160 Mb RAM or greater), Puppy Linux (if 256 Mb or greater), or DSL (if minimal RAM, limited hard drive space, running from a USBdrive, or running from within another OS).
A user may experience problems dual-booting Ubuntu and Windows.
In general, a Windows OS should be installed first, because its bootloader is very particular.
A default Windows installation usually occupies the entire hard drive, so the main Windows partition needs to be shrunk, creating free space for the Ubuntu partitions.
(You should clean up unnecessary files and defragment the drive before resizing.) See changing the Windows partition size.
After shrinking a Windows partition, you should reboot once into Windows prior to installing Ubuntu or further manipulating the partitions.
This allows the Windows system to automatically rescan the newly-resized partition (using chkdsk in XP or other utilities in more recent versions of Windows) and write changes to its own bootup files.
(If you forget to do this, you may later have to repair the Windows partition bootup files manually using the Windows Recovery Console.) Newer installations of Windows use two primary partitions (a small Windows boot partition and a large Windows OS partition).
An Ubuntu Linux installation also requires two partitions -- a linux-swap partition and the OS partition.
The Linux partitions can either be two primary partitions or can be two logical partitions within an extended partition.