Problem need fixed ASAP

I got the Blue Screen Of Death last week, and since then i wrote a couple o java programs and tried to compile them as i usually would and i get the error:

 Registrykey'software/javasoft/java runtime enviroment/current version has value "1.6"but 1.5 is required

Error: could not ind java.dll

Error:  could notfind java 2 runtime environment

now i downloaded all these things but its still saying the same i dont know what to do