they do not go in program files,they go in your AH2 folder,put the .mis file in your misstemp folder.
put the mission .res in your missres folder.
if you have the current version of AH2 then they should work.
if the mission comes with a terrain it goes in your ahiiterr folder along with any .fla or .fld files ,make sure you have AH2 version 2.16