I use Acid Pro myself, but they also have a (free) "lite" version called AcidExpress (look on the sidebar).

If you go to AcidPlanet you can download an 8Pack each week - [An 8pack project is an ACID file that includes eight loops arranged into a song. 8pack projects illustrate how a song is constructed in ACID software, and how easy it is to combine loops ]

great way to build up a loop library

:)
retrocity