Java APIs

Hello all, if anyone could help me here I would be eternally grateful. I have been using a chat room with a java applet now for years and years. I recently got a browser hijacker which I removed (eventually) usingHijack this and Sw Shredder. Since doing this my computer will not recognise that I have java on my computer and thus I am locked out of my favourite chat room. I have tried everything. I have java enabled in my security settings I have downloaded not only the Sun Java VM but also the microsoft one.
When i try to find any of them using Start/Run/wjview I get the error "Error Could not locate Java Virtual Machone: Class not registered"
If i try to get into my chat room a box opens which says "To view this page you need to download and install the following components.....Java Virtual Machine"
I have done everything and still nothing.
Any ideas??