Ok, how the hell did you get that to work in VB?! Vb does not support does not support dynamic dll loading.
2nd: Let the app remember the current plugin directory when rechoosing it.
3rd: Try to automat it. Some people might not know what it is. Use my wrapper sample code, it makes it easier.
4th: Remove the "for Project64" text when showing settings. The plugins aren't always for pj, y'know.
Otherwise it's looking good, for whatever it might be good for...