ACN_Pilot
Were these songs bought from another online store (i.e. Napster, Rhapsody etc.)? If so, and where your licence allows, you may be able to first burn them to a CD then re-import them into iTunes. Be sure when you do, that you check the options available in your software and burn them in a 'lossless' audio format such as AIFF or WAV, otherwise you may experience degradation in the audio quality.
Each store uses their own copy-protected versions of the various audio formats (mp3, AAC, Real Audio) and they are incompatible with each other, so precluding 'direct' copying in most cases. Hope this helps.
Jx