'... but it never lets me install it ...' - implies that 'aim.bin' is at fault, it is not. A '.bin' file is not self executable; thus, the need of a de-encoding / de-compression application - such as 'StuffIt Expander, SE.
Determine if you have SE installed. If so, and if it is not also on the 'Dock', add it - to the 'Dock'.
If SE is no longer installed, then download it (SE) as per Giagara's post's link.
Drag 'aim.bin' onto the 'Dock' based 'StuffIt Expander', for it to be properly de-compressed..
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If SE is indeed installed, then - it appears that your MacOS X experienced a hiccup and no longer has an association between '.bin' files and 'StuffIt Expander'.
You should click once on the 'aim.bin' file, do a 'Command I' ('Finder's 'File, Get Info' menu item), select 'StuffIt Expander' from the 'Open with:'s panel's popup menu (or locate it - in the '/Applications/Utilities/' folder via the 'Other...' menu item), then click on the 'Open with:' panel's 'Change All...' button and click its respective 'Continue' button. This way, all future double-click'ing on any '.bin' file will have 'StuffIt Expander' automatically launch and process the file accordingly.
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You do understand that the
hypertext of the link in the original post is not valid. The correct link is '
AIM'.