A couple of weeks ago I installed W735EQ in XP and everything was flawlessly. Today I'm trying to do it on my new x64 system, but I have this message when I'm uploading the W735EQ.AUT file: "The file you have uploaded is too large. Please upload a valid challenge file". ???
You don't upload the aut file, just put the aut file with the 64bit ser file. When you open the plugin for the first time it generates a ser file. Use the same aut file that you used with your 32bit W735 and put it with the 64bit ser, usually wherever the dll is (wherever you installed the 64bit plugin). You shouldn't have to reauthorize it again. The aut file is what is sent back to you after you upload the ser file.
The same aut file will only work if the hardware is the same....sounds like you have a completely new machine so you'll need to delete both ser & aut files on the new intall, then open W735 which will create a new ser bsed on your hardware. Upload this to the site to enable download of a new authorisation for your 64bit system.