A few months ago I got a virus and my AV was unable to quarantine or delete the file so I just chose a restore checkpoint I believe is was 4 days prior. Just by chance I happen to update Java in those 4 days and when I did the restore I lost the installer package that is needed to remove it. I have tried to download the same version of Java and reinstall it but it always asks for the jre 1.6.0_18.msi which is a resource that does not exist on my hard drive. I can't find a download for just the installer package and I can't unpack the installer without being able to remove this old version so I am a bit confused.
To make the long story short, you just want to uninstall Java (I assume its JRE you're referring to), right? You can uninstall it the same way as other programs do. Go to the control panel -> programs -> programs and features then select Java(TM) 6 Update 18 and click the uninstall button.
I had to forcibly remove it with Perfect Uninstaller, the Control Panel did not work because it needed the installer package. Perfect Uninstaller removed it from the registry and then I had to manually delete all the files from the computer but nonetheless it is over with!