Extract and run IrfanViewPortable.
Additional Plugins included.
Additional languages: download ZIP and extract in IrfanViewPortable\App\IrfanView\Languages then run IrfanViewPortable and Options/Change language...
SaveDir in portable folder: if you don't want: edit IrfanViewPortable.ini.
JPM and JP2 format export registered.
Settings of installed IrfanView should be preserved.