Sinclair Spectrum Game Data Formats:
A repository for the collection of game data formats for old
Sinclair games.
http://www.icemark.com/dataformats/index.html
XeNTaX's MultiEx:
MultiEx allows you to extract and import files from over 90 game
data formats (including HOG, PAK, WAD, and SFX).
http://www.xentax.com/html/multiex-main.htm
