Wrong song info

Hi,

I have some songs on my computer than no matter how many times I go into the
actual file and edit the infi by clicking the properties tab media player
keeps changing it back. whats realy irating is they are all by different
artists but it keeps putting them together as one artist(one of the songs is
by that artist). It's driving me crazing I realy want to get these files
fixed before I download itunes for a nano I'm getting. Does anyone have any
advice?