Changing audio format

Ok, so I just got a PSP for Christmas. However, I dont really like any of the games out for it, and I dont feel like wasting money on UMD movies. But because I've always wanted one, but will never be able to aford one, I'm using my PSP as a sort of PDA. My queston however is this:

How/Can I change the format of an audio file from something not MP3, to MP3?

I have a lot of music on my computer that I've ripped from my CD collection and/or downloaded, and I'd like to put some on my PSP. My only problem is, all my riped music isn't in MP3 format, which is the only thing my PSP supports (that I know of). So I'd like to know if there is a way to change the files into an MP3 to my PSP CAN play them.

What format are they already in?

All I get when I look in properties is "Windows Media Audio format" Is that what you need to know?

I am assuming that all the music ripped is in WMA (Windows Media Audio)format so I give you this site http://www.wma-mp3.com/

Now, too make sure you don't have to keep rencoding all your future ripped music I will tell you how to change the format the WMP will rip the music too.

Open Windows Media player, goto Tools on the menu bar, scroll down to Options.. and click, Goto the Rip Music tab and then down to the Format dropdown list and there should be Mp3 at the bottom of the list.