For those of you resigning EBOOT's for 4.21 use, I noticed that the content id can be gotten from the EBOOT itself rather than having to use PKG_ContentID.
So if you no longer have the pkg file, here's a small program I wrote up to get the content id from the eboot file.
Just drag the EBOOT.BIN onto the file "get_content_id.exe". I included the c source file in case anyone was interested.
http://www.4shared.com/zip/ebSDQR2r/get_content_id.html