AMDIS is truly a great program and the mass spectral deconvolution algorithm transformed (together with LECO's ChromaTOF) the whole GC-MS data processing business. The *.FIN and *.ELU are the target and component result files created by AMDIS. They are ASCII files, so you can open them with TextPad, NotePad++ or EMEditor and actually edit or parse them. Lots of secondary data processing tools make use of that. Here is a list of files that are created by AMDIS and their meaning:

*.MSL Unique Target Compounds Library

*.CID Common Compound Information Library

*.FIN target result files

*.ELU component result files

*.CSL Calibration & Standards Library

*.CAL RI Calibration Data file

*.ISL Internal Standards Library

*.RES Settings and Config File

*.MSP Mass Spectral Transfer File

BTW, the AMDIS_HELP.chm has great tutorials about the inner workings and sometimes also more information about the cryptic meanings of variables.

Hope this helps.