>I'm using some .png images in forms, and when i build the project the second or third time vfp ( 8 and 9 ) hung up, I prove in more than one PC and i have the same problem.
>Any solution to this ? or I need to convert the files to .bmp

What VFP version are you using? In VFP9 there's a bug VFP hangs rebuilding app with cached GDI resource fixed in SP1 beta. A workaround is to issue CLEAR RESOURCES before build.