when using limewire my cpu uasage goes to 100% and the computer becomes very slow -computer guy said this is a problem in limewire not with the computer -help-

Try updating your Java. Use the JRE (Java Runtime Environment) offline installer & remove any other Java versions installed on your computer (via control panel > add/remove programs) before installing the new version.
Java SE Downloads

If changing Java versions doesn't help, in LW go tools > options > advanced > performance > disable DHT capabilities, disable TLS capabilities, disable ultrapeer capablilities > apply > ok. See if that makes any difference.