We all have to start somewhere. So, if you are interesting in 'having a go' at computer forensics, here's a quick, practical introduction to the mechanics:

http://www.shortinfosec.net/2008/07/tutorial-computer-forensics-process-...

The open source tools mentioned in this article will enable you to get up and running with a 'forensics learning lab' that you can use for self instruction and practice.  The Helix live CD in paricular provides a collection of forensics tools that can be used for this purpose at least:

http://www.e-fense.com/helix/