Microsoft office personal edition 2003

Question

i uninstalled the microsoft office personal edition 2003 japanese version in my pc because i wanted to replace it with microsoft office 2007 version...But the 2007 version can not be installed. So i reinstalled the 2003 again, inserting the disk...but it doesnt install too. After i insert the disk, many files in rar format came out. I dont know what to open. The window installer ran but it says, can not access, and looking for package. I have my serial key, but it wasn't asking for serial key. It just says can not access the package.