The process of capturing the memory is known as dumping. The tools and methods of dumping the memory on a running computer differ with the Operating System.

Eg.

Windows

To dump the memory here we are using dd.exe tool which is available

The command for dumping is:-

C:\users\shailendra>dd.exe if=\\.\PhysicalDrive0 of=d:\images\PhysicalDrive0.img conv=noerror

The command conv=noerror will make the dumping of memory forcefully.

To write the dump image on to hard disk you need to add --localwrt.

This tool is not useful for the windows os which are after 2003 sp1 or Vesta.

There are few tools available just for dumping memory.

mdd.exe from Mandiant is for windows
memdump for linux

Mandiant also released a new tool "Memoryze recently. More info can be found at

http://holisticinfosec.org/toolsmith/docs/february2009.pdf

Hope this help

VJ