Experiment, experiment, experiment.... each person on this board has his/her own favourite plugin settings. Find the one that works best for you. Heck, even each game has its own 'best' plugin settings.
Looking at your specs, I'll try the following for the 'base' configuration:
Video: Pete's OpenGL (since you got a GeForce3)
CDROM: ePSXe internal (Pete's also works pretty well)
Sound: ePSXe internal (not the best, but it works)
Experiment with the Sound plugin.... there's Iori's, Null's, and many others.... search this board for other recommendations. There have been quite a number of topic on this already.
I'm having a problem with configuring the plugin (pete's openGL), when i go to configure the video plugin the field where they go is empty (even tho i put the plugin in the plugin folder) , so i tried to enter the path manually, but it still doesn't recodnise it.
Nitrous Oxide: Make sure that the shortcut that you use to start ePSXe has the 'Start In' folder set to ePSXe's folder (right click your shortcut and choose properties, then choose the shortcut tab, then copy the information from the 'Target' box to the 'Start In' box and dont forget to take epsxe.exe off the end). Then hopefully you should then see your plugins listed.