If you want good
help, post the error messages you were seeing. Copying jfantom.dll around probably made it worse, instead of better. You should definitely undo your changes.
My crystal ball (I bought mine from a very talented fortune teller) tells me, that you're using a 64 Bit Windows, and that you installed a 64 Bit JDK instead of a 32 Bit one. Currently, only 32Bit Java is supported. So I bet that the first error message was about the fact that a 64 Bit jfantom.dll doesn't exist, simply because we don't supply any because 64 Bit applications aren't supported by Lego. After creating a copy of jfantom.dll, the error message might have been that the jfantom.dll (which is 32 Bit) is incompatible with the 64 Bit JDK that you are using.
Install a 32 Bit JDK and set the LEJOS_NXT_JAVA_HOME environment variable to the root directory of the 32 Bit JDK. Also make sure that the latest fantom driver (1.1.3) is installed. It is available here: http://mindstorms.lego.com/en-us/suppor ... river.aspx
. In case you're using Eclipse, download a 32 Bit edition of Eclipse.