Try this :
Make a default unmodified Project64 , i see you're using 2.3, i'm using 2.1 but i don't think it would make a difference.
Now it's important so make sure :
- the Project64.cht file from Showdown64 is in
...\yourP64directory\Config\
- the WWF No Mercy.fla and WWF No Mercy.mpk files from Showdown64 are in
...\yourP64directory\Save\
- there is a "hires_texture" folder is in
...\yourP64directory\Plugin\GFX\
- the WWF No Mercy folder that contain all the Showdown64 textures is in
...\yourP64directory\Plugin\GFX\hires_texture\
so it looks like by example for the AJ Styles textures
...\yourP64directory\Plugin\GFX\hires_texture\WWF No Mercy\Roster\AJ Styles\
- make sure the WWF No Mercy.z64 rom is in (IMPORTANT : it must be the rom 1.0 , not the rom 1.1 or the mod will not work as the memory addresses required by the cheat file aren't the same)
...\yourP64directory\Rom\
- make sure you have patched the WWF No Mercy.z64 rom according to the "1-Patching your ROM file" from the 1st post of this thread in the "Instruction and Download" section.
Personnally i patched with LunarIPS without problem.
Now launch Project64
- Click on File -> Choose Rom Directory and select the correct rom directory (in case you have several Project64 directories, if you don't choose the one from your Showdown64 powered P64 , the game may then not load the correct patched No Mercy rom)
- Click on Options -> Settings
At "Directories" make sure it looks like this :
(Project 64 2.1 SH64 is the name of my P64 + Showdown64 folder as i have several P64 directories each with a different mod for No Mercy, your own P64 directory name may then be different)
- Click on Options -> Settings
At "Plugins" make sure it looks like that :
(the important one is the Jabo 1.7 plugin as it's what is going to replace textures by the SH64 ones)
- Click on Options -> Settings
At "Advanced make sure "Remember Selected Cheats" is enabled so you don't have to re-enable the cheats after every P64 launch
- in the Rom list on the main P64 window, Right Click on WWF No Mercy and click on "Edit Cheat"
Enable only the "Showdown64" cheats
But read this post from Chuckiepk for specific cheats you need to disable to avoid a nasty freeze problem when a wrestler is out of the ring
http://s4.zetaboards.com/Old_Skool_Reunion/single/?p=10003624&t=10005574
That should be all, if you have set up everything correctly , you will enjoy Showdown64 in its full glory.