how come when i search for songs the only results i get are mp3 files. when i first started using lime wire i could download just regular music files that could be burned and played in any cd player not just those players that can also play mp3s?

The "regular" files you were downlding would have been mp3 files. You can also downld other formats like aac (m4a), mp4, ogg, wma (eek!), & the odd lossless format.
Perhaps you've forgotten about this: Burning an audio CD from your MP3's

If you've downlded mp3 files you can't play or burn then it sounds like you're missing the appropriate codec, id3 tag or they're corrupt. See T3 Spammers; mp3 Bit-Rates Versus File Sizes