iTunes help.
 

When my wife got an iPhone I set up a seperate partition on her computer hard drive to accommodate iTunes and her music collection.
Apparently at some stage during an iTunes update it reset the download location I had set to the default location buried deep in the bowels of the documents and settings folder on the C drive.
As a result subsequent downloads have been slowly filling the C drive to capacity and it has got to the stage that the computer has difficulty doing anything.
Can I simply move the files from their location on the C drive to the preferred location on the M (Music) drive and if so will iTunes find them next time it runs?

Can it be that simple?

You should be able to find the iTunes library file on your HDD and move that to another partition. Next time you open iTunes just point it to the (now moved) library file.