I browsed around Microsoft's website and found an article describing IE 5.0 in WINNT 3.51, but there was no mention of IE 5.5. The corresponding IEAK 5.5 can't run under 3.51 either; it can only work with 5.0.
Also, Microsoft's approach is that no matter which version of IE, just download one SETUP file and run it when connected to the Internet, and it will automatically download the installation files corresponding to the Windows version.
According to Microsoft, the IE files of the same version number for different platforms are not interchangeable, so I think I can only give this a try.
The following is an excerpt from the Microsoft Internet Explorer 5 Resource Kit, including information about the 16-bit platform. The gist is that the dial-up program for 3.1 can't be used in 3.51, and also that IE 5 supports long file names while the 16-bit platform doesn't, which can cause problems when referencing files.
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Dial-up access—If your users need dial-up access, you must include the Stack and Dialer for Windows 3.1 as part of your setup package. If some users are running Windows NT 3.51 and some are running Windows 3.x, you should include at least two installation options: one with the dialer for Windows 3.1 and Windows for Workgroups 3.11, and one without it for Windows NT 3.51. For dial-up access, you must first configure Windows NT 3.51 computers for Remote Access Service (RAS).
[ Last edited by fdsiuha on 2005-11-3 at 23:44 ]