try deleting the folder in TDATA and the same folder in UDATA(i don't remember the number exactly 4d530064??)... You will lose your profile and game save. with both folders deleted start up halo and make up your profile again, go to system link and create a new game when choosing a map Foundation should NOT appear. Ok reset and boot off the update cd...install only the updater no maps yet. reset the box and do the renaming stuff... now go back to halo2 and create another game in system link,, if you can choose the foundation map then it got installed properly. Now you should be able to go the the update cd one last time and install both the map packs and they should work... When i did this i put the updater cd right on my E drive and used avalaunch or xbmc to do all the file name changing.
If that doesn't work, try deleting the folders in UDATA and TDATA and delete your game off the F Drive and start form scratch.
Good luck.