UnsupportedClassVersionError

Hi,
I am having library jar file which is compiled with jdk 1.3 version.My application is running in jdk 1.4.When i am trying to run the files from the library i am getting the following error.

java.lang.UnsupportedClassVersionError: (Unsupported major.minor version 48.0)

Please help me in resolving this issue.

Also library source code is not with me and hence recomiling with jdk 1. 4 is not possible

Your problem must be the other way around; old class files work just fine with new JDKs, but class files compiled on a new JDK won't, by default, work with some older ones. Try typing "java -version" to make sure of the Java version you're running when you run the application. Please don't tell me you already know what it will say -- you might be surprised!

Thankx for your reply,
I checked the Major version of the library class file and the project file.

Library Class file Major Version : 45 --JDK 1.1
project class file Major Version : 48 --JDK 1.4

I am able to load and run both the class files if my WSAD JDK is 1.3.But if i change my compiler settings to JDK 1.4 i am getting unsupported class version error.