Hi,
make sure you have the latest version 7.3 off of their website and get Jabos D3D plugin v1.4 from project 64s installation and place it into the plugin directory.
Now choose plugins and select it, make sure that you have a reasonable resolution etc selected dependent upon your system specs (You need a minimum of about a PII 450 and TNT card I think with about 128megs memory), choose jabos or nrages input plugin and configure and now play!
Choose D3D7 + transform and lighting in the graphics plugin options if you have a good card!!!!
And also make sure no other shit is running in the background like virus checkers etc...
You should also post your system specs to these guys as they can help a lot more if you give useful information

!!!!!!!!!!!
MartyMcFly
Edit: heh, i just noticed u posted while i was writing this

yep, u definatly need to change your default plugins (As i said, Jabo D3D 7 graphics, Jabo or NRage Controller plugin and Azimer Audio HLE 4.0 beta 1/2) Get the jabo plugins from the
www.pj64.net release of project 64