99% of the 100-odd hours of music on my computer is saved as .WMA files (I chose to record my music onto my computer as .WMAs over .MP3s because space is of no concern to me (119GB, baby!)) and I was wondering if there's an easy way of converting all the files to MP3s? The only way I can think is to re-record the CDs onto the computer as .MP3s but with so much music, this would take weeks.
The type of software you are looking for is generally known as a 'ripper'. Just search download sites for 'mp3 ripper' or just 'ripper' and you should find plenty.