Vmware Server

Begin enjoying the benefits of server virtualization with the free VMware Server. VMware Server installs on any existing server hardware and partitions a physical server into multiple virtual machines by abstracting processor, memory, storage and networking resources, giving you greater hardware utilization and flexibility. Streamline software development and testing and simplify server provisioning as you utilize the ability to "build once, deploy many times."

http://www.vmware.com/products/server/

Windirstat

WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows (all current variants).

http://windirstat.sourceforge.net/