i was working on a head mesh the other day. now every time i start a new blend the head is there and not the cube

Are you using Blender 2.5x? If so you can get the initial settings back by going to File > Load Factory Settings (no idea if it works for 2.49, maybe it does). You will lose any personal configurations you had made to those settings though.

It sounds like you accidentally hit ctrl U; which saves the CURRENT SCENE as the default file. I recommend opening a new file (the head will show up) delete the head, replace with a cube at center, change any other useful settings you regularly have to change (sky color for instance) and then hit ctrl U and confirm. Now your new files will all start like this.