It's not memory - it's called hard disk space. Memory is an entirely different hardware component which stores Windows & running programs temporarily
while you are using them, whereas disk space is where you permanently
install Windows & programs and write your own files.
To increase free space you will have to uninstall applications you don't use. If you have already done that but still don't have enough free space, you will have to replace the drive with one that has a larger capacity.
You don't say which version of Windows, but if it's XP or later you could disable "System Restore". This will make more free space avialable by removing all the 'restore points' which can often take up several gigabytes. However, just be sure that you won't mind not having SR to fall back when Windows gets messed up.
Edited by phillipcorcoran, 03 August 2010 - 04:37 AM.