Okay, I've split them using 7-zip and added the extension zip to fool the filter.
To reconstitute:
1) Rename all three files, removing the ".zip". Now the files should have the extensions: .7z.001, .7z.002, .7z.003
2) Extract any of the three files with 7-zip
Edit:
Attachments (HSsounds_english_1_0.7z.001 - 003) lost in the crash of 2009; use this FileFront link instead - WEK