If you already have v1.01 Shareware OR Registered, you can download the patch 1.01 to 1.06 here. To patch your existing version, you should copy this file (q101-106.zip) to your \quake directory. Then upzip it, and answer 'y' to overwrite the existing file 'quake.exe'. Once it is finished unzipping, run the file 'patch.exe' from this same directory. Once you are sure it worked, you can delete the q101-106.zip and patch.exe files if you want to.

Here is a list of the fixes and changes in the v1.06 release.

If you already have v 1.01, you can download the patch from 1.01 to 1.06 here.